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The Kostüme Unisex Knee Warmers are from a limited edition collection (Kostüme calls it an #edit) and made from recycled materials. With fluffy insides for chillier rides, their USP is that the silicone of the leg gripper is designed to grip your shorts and not your delicate cyclist's thighs like most other warmers. It's a different way of doing things that isn't without its issues. The fit might also be a problem.
If you want a bit more protection, check out our guide to the best arm and leg warmers.
I am in a constant search for the perfect knee warmer. The ones I have collected over the years have their own large compartment in my wardrobe, and each pair has their particular merits but not one is absolutely perfect. My current faves are a pair I picked up for £15 in a sale from a manufacturer better known for bikes than clothing. It's a simple clothing accessory but not so easy to get right (if you're as finicky as me), so when Kostüme said it had developed a new knee warmer that was completely different to anything out there, I was immediately interested.
For such a simple garment the Kostüme knee warmers pack a lot in. The 90mm-deep thigh gripper is made from upcycled Lycra off-cuts from its bib shorts and has a 50mm band of silicone grippers that are unconventionally on the outside and designed to grip the shorts instead of the leg. They sport reflective tags on the front of the warmer not the back, but they do carry handy leg orientation information. While incredibly comfortable and warm, their fit isn't ideal, and their unique gripper system doesn't always work.
Kostüme makes technically innovative cycling apparel that combines all-day performance, comfort and utility with exclusive artist collaborations and obsessive attention to detail, it says here. Developed in England and made from premium recycled materials in Europe by independent, family-run factories with decades of experience, the kit is only available to order, and released in strictly limited edition batches which Kostüme likes to call #edits.
The company is keen on environmental responsibility, and with only the products ordered by customers getting made it ensures there's no waste, no unwanted stock, no damaging sales, and no unsold products destroyed or sent to landfill, which have all got to be Good Things. Kostüme limits the number of products available in each of its #edits to just 350.
The main material of the knee warmer is a GRS-certified recycled fabric with a brushed-back microfibre finish. Global Recycle Standard (GRS) is a certification promoted by Textile Exchange with the aim of encouraging the use of recycled materials in the textile sector. It's a Roubaix-style material with a nice soft and fluffy inside, which makes them great for when you might think about cosseting your knees in a warmer. Kostüme rates these for 2-12°C, although I'm well into longs towards the bottom of the scale. Your mileage, ability to deal with the chill and how much you care for your joints may vary.
For when I'm likely to be using a knee warmer, which is at the beginning or end of a ride, and sometimes all day in changeable conditions if the temperature is just about managing to stay in the double digits, they felt just right. They don't claim any water resistance, but I've never felt that I've needed that in a knee warmer.
Kostüme has done a great job with the whole feel of the knee warmer and it's a pleasure to slip on. It has a three-panel ergonomic construction, with one of those panels well tailored to stretch along the top of the thigh and over the front of the knee. Kostüme says this allows it to reduce the amount of fabric used on the rear of the warmer, which helps to limit bunching behind the knee when pedalling, but in use I found that to not be the case. More on that later.
The warmers come with neat reflective tabs on the bottom, but in complete contrast to most other knee warmers (and shorts and 3/4s and tights) that feature reflective tabs, these have been placed on the front of the leg rather than on the back. This was the subject of much ride debate, and the consensus was that it's not going to make much difference because while reflective tabs are nice to have, it's but a cursory nod to safety, and probably best not to be relied upon to keep you safe.
To ensure that you get the knee warmers on the right way round and on the correct leg, these reflective tabs have the designated leg and orientation printed on them, which is most probably why they're on the front, and it does save a bit of time when putting them on if that sort of thing confuses you.
The big deal with these Kostüme knee warmers is how they stay up. Most knee warmers rely on some sort of gripper that holds onto the skin of the thigh, be that in the form of a bit of elasticated fabric, or some kind of silicone gripper, or both. For a lot of people the compression needed to keep the knee warmer up can lead to unsightly sausage leg, and the silicone used in some grippers can provoke a rash or welt; I've experienced the latter with some warmers.
Kostüme has flipped traditional thinking on its head and put the silicone on the outside of the warmer so it sticks to the shorts rather than your delicate cycling thighs. As I said earlier, the whole thigh gripper section is made from an off-cut of its bib shorts fabric which is lightweight, does a great job of reducing bulk and is a considerable 90mm deep, with the top 50mm of that decorated with a fine pattern of grippy silicone dots on the outside.
It's certainly a different way of thinking and an intriguing concept, and to a large degree it does work. The upcycled fabric on its own does a fine job of holding onto your thigh; its width and the choice of fabric is an effective way to get the warmer to be snug without any squishing of flesh to cause the dreaded sausage leg. The efficacy of the silicone dots on the outside of the warmer does depend somewhat on the tightness of the shorts you're wearing. With those that had good compression to them the knee warmers stayed securely in place, but swapping to some that were not as constrictive highlighted that the Kostüme warmers did like to gently slither down over the course of a few hours.
Because the thigh gripper is such a thin material with no hem, which is actually very lovely, it can unfortunately be too easy for the top to roll over when pulling your shorts leg over them, causing a thin ridge underneath, which may or may not bother you, so that takes a little care to get just so.
Tension at the bottom of the knee warmer is achieved by the fabric folded over itself 15mm, which is enough to hold the warmer close to the calf but not too tight to be constrictive or allow some movement.
Sizing of the knee warmers is based around the widest part of the thigh and then the length of the inside leg from crotch to inner ankle bone. That put me right in the middle of medium for the thigh and yet off the bottom of the small for the leg length. I opted for medium as I'm usually that size in all my other clothes, including knee warmers, and I'd rather have a longer knee warmer than a more restrictive thigh. I tried to stretch a tape measure around my thigh (steady now) to the maximum circumference of the small warmer and it wouldn't go.
Kostüme is keen for you to take time to get your measurements right as shipping and returns harm the environment, but it does say that its sizes are fractionally larger than most brands, offering a highly technical tailored construction that focuses on comfort over aero performance. So if you prefer a race fit you might benefit from sizing down. Or just print real life sizing guides.
Sensually, slipping them on they feel gorgeous. All the fabrics are top quality, the inner material is cosy fluffy, all the seams are flatlock stitched and the wide but thin Lycra material up top is compressive without being tight and bulge inducing. The tailored panel wrapped perfectly over the top of my knee and the length of the mediums meant they extended well down the calf, which is where I like it.
Unfortunately the fit in between the top and the bottom of the warmers wasn't very good, and while fine upon initial dressing and stood upright, they became uncommonly loose on the bike, and baggy around the back of the knee. While not uncomfortable, it was annoying and, let's say it, unsightly. I think a large part of the issue is that there isn't much taper from thigh to the calf; there's not enough shape or elasticity in the fabric to deal with the significant width difference between a cycling thigh down to a bony knee and then back out to a shapely calf muscle again.
There's also no tailored anatomical curve to the knee warmers, as is common on similar pieces, so they struggle to deal with the flexings of a bent knee, and there's significant wrinkly slack in the rear.
While the part of the Kostüme knee warmer that wrapped around my thighs felt perfect, from the narrowing to the knee and below they felt on the large side, so check the size chart and size down if in any doubt.
The Kostüme warmers are cheaper than the Pactimo Alpine Thermal RT Knee Warmers Iwein tested last year, that were deemed pricey at £53 for what they were, which is a little short and without any weather protection.
The Specialized Thermal knee warmers that Emma tested in 2021 (when they were called Therminal) are a little cheaper at £30; they're light and well cut, and come in six sizes. They're not weatherproof, either, and Emma had doubts about their longevity.
For the same price you can opt for the Rapha Thermal Knee Warmers. Like the Kostüme warmers they have a brushed back inner and come with pink tabs on the outside to let you know which goes on which leg. Although the gripper is not as wide, they do look to be more tailored to a leg below the thigh.
Knee warmers that take an environmentally responsible and different way of doing things, some good, some less so
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road.cc test report
Make and model: Kostume Unisex Knee Warmers
Size tested: Medium
Tell us what the product is for
Kostüme says: "Our signature knee warmers apply the same design principles and cutting-edge recycled fabrics as our arm and neck warmers, to create a new standard in three-season protection for cool and changeable conditions
"Discomfort lives long in the memory, and few riders will forget the experience of wearing a badly-fitted knee warmer miles from home. As with our arm and neck warmers, the GRS-certified recycled main fabric plays a key role, with the brushed-back microfibre finish retaining a warm feeling on the skin even when wet - essential in an area directly in the firing line of front wheel splash damage. The 3-panel ergonomic construction allows us to reduce the amount of fabric used on the rear of the warmer, which helps to limit bunching behind the knee when pedalling. This is the key source of rubbing for knee warmers and cycling tights.
"The other common irritation is the impact of grippy silicone on delicate - often hairy - inner thighs. We've solved this by literally flipping the traditional thinking and printing them on the outside of the fabric, so that it adheres to the inside of your short instead of your sensitive legs. The same kind of why-hasn't-it-been-done-before thinking extends to the handy front/left/right indicator on the reflective strip, meaning you'll hopefully never put a warmer on the wrong leg again. As a final nod to comfort, we've printed the thigh gripper on an extra-wide offcut of our amazing bib short fabric, which also reduces bulk."
Tell us some more about the technical aspects of the product?
Kostüme lists these details:
Bluesign® and OEKO-TEX® certified recycled brushed-back main fabric
Articulated 3-panel construction for ergonomic fit
External silicone thigh gripper grabs your shorts, not your leg
Flatlock seams for comfort and performance
Handy left/right indicators
Reflective tabs and transfers to aid night safety
Optimal temperature range 2-12c
Made in Romania
Main - 86% recycled polyester 14% elastane
Contrast - 65% recycled polyamide 35% elastane
Wash at max 30°c Delicate cycle/spin
DO NOT bleach, tumble dry, iron, dry clean or use fabric softener
Well made with flatlock seams everywhere; an extra point for recycled fabric and using shorts fabric offcuts.
The fluffy insides of the main body was just right for the weather conditions in which a knee warmer is likely to be used, but the shape and fit detract from their character.
Minimal tapering between top and bottom and non-anatomical tailoring to deal with knee bend severely compromised fit.
Double triple check your sizing and maybe size down; even then they might not fit in some places.
For a Roubaix style material, they're nice and light.
The wide gripper and choice of materials makes these a supremely comfortable accessory.
The price puts these Kostüme knee warmers in with the Rapha/Castelli/Assos crowd, but the company has added to the humble knee warmer with a different way of thinking, and has used recycled fabrics and off-cuts to be eco friendly, which adds value in my opinion.
How easy is the product to care for? How did it respond to being washed?
Thrown in with the rest of the cycling kit at 30 degrees; no issues to report.
Tell us how the product performed overall when used for its designed purpose
There's not much that can go drastically wrong with a knee warmer. These Kostüme ones were warm and long enough to keep things toasty, the wide fabric of the thigh gripper was great, but the outside silicone gripper system wasn't so perfect, and fit might be an issue.
Tell us what you particularly liked about the product
Wide thigh gripper, warm material, planet-friendly manufacture.
Tell us what you particularly disliked about the product
Sizing, shape and cut was off on me, meaning it went very baggy around the knee.
How does the price compare to that of similar products in the market, including ones recently tested on road.cc?
They're cheaper than the Pactimo Alpine Thermal RT Knee Warmers that were deemed pricey for what they are, which is a little short and without any weather protection, and £53.
The Specialized Thermal knee warmers come in at £30; they're lightweight and well cut and come in six sizes, but in our test of the previous version (Therminals), Emma was concerned about their longevity.
The Rapha Thermal Knee Warmers are the same price as the Kostüme warmers, and have a brushed back inner and come with pink tabs on the outside to let you know which goes on which leg. Although the gripper is not as wide, they do look to be more tailored to a leg below the thigh.
Also similarly priced are the Castelli Thermoflex 2 Knee Warmers (£42) which are warm, stretchy and tailored, and if you've got a bit more to spend the Nano Flex 3G Knee Warmer is a water-repellent version for £50.
Did you enjoy using the product? I liked the theory, the practice not really; the bagginess around the knee was annoying.
Would you consider buying the product? No
Would you recommend the product to a friend? If they had issues with other brands' silicone grippers yes; I'd say double check the sizing, though.
Use this box to explain your overall score
There's a lot to like about the Kostüme Knee Warmers. The company's firm eco stance with the recycled fabric of the main body is a good thing and it feels great too; the wide thigh gripper made from its shorts offcuts is also a good thing and it's incredibly comfortable and contributes to zero sausage leg. If you react to the silicone grippers of other knee warmers against your skin then you'll appreciate Kostüme's about face approach with that system – just make sure your shorts are snug enough. The tailoring and fit let them down, though.
About the tester
I usually ride: It varies as to the season. My best bike is: The one I\'m on at the time
I've been riding for: Over 20 years I ride: Most days I would class myself as: Experienced
I regularly do the following types of riding: road racing, cyclo cross, general fitness riding, fixed/singlespeed, mtb, Fun
Jo Burt has spent the majority of his life riding bikes, drawing bikes and writing about bikes. When he's not scribbling pictures for the whole gamut of cycling media he writes words about them for road.cc and when he's not doing either of those he's pedaling. Then in whatever spare minutes there are in between he's agonizing over getting his socks, cycling cap and bar-tape to coordinate just so. And is quietly disappointed that yours don't He rides and races road bikes a bit, cyclo-cross bikes a lot and mountainbikes a fair bit too. Would rather be up a mountain.