Like this site? Help us to make it better.


Gemini Juno 100 rear light



Superbright light that gets attention without burning eyes or your bank balance
Very bright, but kind on the eyes
Versatile mount
Easy to use
Run-times shorter than claimed
Rotating mount could be better

At every product is thoroughly tested for as long as it takes to get a proper insight into how well it works. Our reviewers are experienced cyclists that we trust to be objective. While we strive to ensure that opinions expressed are backed up by facts, reviews are by their nature an informed opinion, not a definitive verdict. We don't intentionally try to break anything (except locks) but we do try to look for weak points in any design. The overall score is not just an average of the other scores: it reflects both a product's function and value – with value determined by how a product compares with items of similar spec, quality, and price.

What the scores mean

Good scores are more common than bad, because fortunately good products are more common than bad.

  • Exceptional
  • Excellent
  • Very Good
  • Good
  • Quite good
  • Average
  • Not so good
  • Poor
  • Bad
  • Appalling

The Gemini Juno 100 is a simple, easy to use rear light with few frills, but it does pack some useful features, including a 30 COB LED lighting array that's super-bright without melting eyeballs, and a clip mount that allows it to be attached on or off the bike in a variety of ways. A couple of niggles with the mount, and the run-times aren't up to claims, but otherwise this is a top performer.

High-powered rear lights can be useful for getting attention from passing motorists, but often they can be blinding, even in lower power modes. Having an StVZO-certified light can prevent this; even adjusting the angle of a rear light can help. Gemini's Juno 100 packs a whopping 30 LEDs on a chip-on-board (COB) configuration, which Gemini says 'emits a soft, more diffused light that is easier on the eyes'.

> Find your nearest dealer here

Sadly, I wasn't able to flag down any drivers during my testing period to find out if it works, so instead I simply looked directly at the light in each brightness mode from behind the bike to see what it might be like for a rider following you, for instance when you're on a group ride.

Though I wouldn't say looking at the light in any of the modes was a pleasant experience, it didn't cause me temporary blindness like some lights have done in the past – even in the highest 100-lumen flashing mode.

The oval arrangement of LEDS gives the light a distinctive shape that certainly stands out from the usual lighting crowd, and thanks to the ability to rotate around its base 90 degrees, it can be orientated either in line with your seatpost, or perpendicular to it (more on this later).

2021 Gemini Juno 100 Rear light 3.jpg

The curved lens also gives the light decent side visibility as well, which is a bonus. Although 100 lumens max might not sound as powerful as some, even in bright daylight it really stands out – I honestly don't think you need any more than this to stand out, unless you want to be really obnoxious.

> Check out our 6 tips for cycling at night

The Juno 100 has several modes to play with. In steady mode this consists of high (100 lumens), medium (50 lumens), and low (25 lumens). In flashing mode, it's high, low and strobe.

Operating the light is a doddle – just press the button on the front of the unit to turn it on, and keep pressing the button to cycle through the different outputs. Switching between steady or flashing modes is similarly easy – just double press the button quickly. Handily, when you turn on the light later, it will be in the last mode you used.

Gemini claims up to 24 hours' run-time from a single charge in its lowest power mode of 25 lumens, and up to 4 hours in the highest power mode (though it doesn't state whether this is steady or flashing).

> Buyer’s Guide: 19 of the best rear lights for cycling

In testing, the Juno 100 didn't get anywhere near the maximum run-time in the lowest power flashing mode, with a maximum time of half that – 9 hours 45 minutes to be precise. It fared OK in the high power 100 lumens steady mode, lasting just under 1 hour 20 minutes, at which point it cleverly goes into an automatic battery saving mode, with a low flash giving you a further 5 hours and 40 minutes.

Similarly, in low steady mode it took 3 hours 19 minutes before it went into its default battery saving mode, with the same extra time in low flashing mode.

There's no battery level indicator here – not unusual for a rear light – but instead a small built-in LED goes red when the battery gets low. Charging takes just an hour from empty.

The light unit is solidly built and looks made to last, its poly carbon composite construction could probably take a bit of a licking.

2021 Gemini Juno 100 Rear light 2.jpg

The light can be attached in a number of ways – either via the simple silicone band that allows you to wrap it around a seatpost snugly without it moving around, or using the built-in clip that enables you to attach it to a belt, bag, helmet, or anything else that it might fit. This makes it a great additional light to run alongside your existing rear light for really getting noticed.

As I mentioned earlier, the unit can be rotated around its mount to change up its look to suit whatever you're mounting it to, through 360 degrees, with the light locking in place at 90 degree intervals. This works well, apart from a slight niggle – that being a small amount of play in the mount which means it doesn't always lock into place at exactly 90 degrees, so you often have to manually adjust it a touch to get it to sit straight relative to whatever you've mounted it to. That might sound picky, but if you have neatness OCD like me it'll drive you insane.


Charging is taken care of via an old-school micro USB connector and a cable is bundled in the box. To access the charging port there's a chunky silicone cover which is quite deep and offers solid protection against water ingress – I certainly didn't notice any moisture seeping in after many foul weather rides.

My only gripe with the charging port is that the light needs to be orientated perpendicular to the mount, otherwise it's hard to access. That's nitpicking though, really.

Value and conclusion

At £29.99 the Juno 100 isn't bad value for what you're getting, but you can get 100-lumen rear lights for less. The Magicshine Seemee 100 is £25.99 and has a smart braking mode to make it stand out, though it does weigh 15g more.

Another 100-lumen option comes in the shape of Giant's Recon TL 100 with an almost identical weight, but it's £24.99 and trumps the Juno 100 for run-times, though side visibility could be better.

The Knog Plus Rear Light is even cheaper at £17.99 and is super-lightweight at 18g, but you get a minuscule 20 lumens output, which literally pales in comparison to the Juno 100.

On the other hand, the Lezyne Stick Drive is £30 and has a maximum output of 30 lumens, while the Ravemen TR50 (50 lumens max) is £34.99.

Overall, this is a good looking, eye-catching (in a good way), simple-to-use and versatile light that can be mounted in a variety of ways. The run-times aren't quite as impressive as claimed, though.


Superbright light that gets attention without burning eyes or your bank balance

If you're thinking of buying this product using a cashback deal why not use the Top Cashback page and get some top cashback while helping to support your favourite independent cycling website test report

Make and model: Gemini Juno 100 rear light

Size tested: 100 lumens

Tell us what the light is for, and who it's aimed at. What do the manufacturers say about it? How does that compare to your own feelings about it?

Gemini says, "Increase your visibility and stay safe on the road. Designed for the day-in day-out commute."

Tell us some more about the technical aspects of the light?

Gemini lists:

Brightness 100 Lumens

Battery 2Wh Integrated Battery

Weight 35g

Modes Steady – Low / Med / High

Flash – Low / High/Strobe

Material Poly Carbon Composite

Safety LED Thermal Protection

Charging Protection

Built-in Seatpost and Clip Mount

Silicone Mounting Band

USB Charging Cable

Rate the light for quality of construction:

Build quality of the light unit is excellent, though there's a little play in the rotating mount.

Rate the light for design and ease of use. How simple was the light to use?

Very easy – just one button to adjust all its functions. Just enough modes to keep you happy without being OTT.

Rate the light for the design and usability of the clamping system/s

The mount is very versatile, allowing you to fit it conventionally to a seatpost, or attach it to a belt or bag with the built-in clip. The unit can also be rotated 90 degrees for a different style.

Rate the light for waterproofing. How did it stand up to the elements?

No issues, even when regularly exposed to water and mud.

Rate the light for battery life. How long did it last? How long did it take to recharge?

Not quite as impressive as claimed, but still pretty good nonetheless. Charging time is very quick.

Rate the light for performance:

Super-bright without being painful to look at makes it safe for other road users; 100 lumens is plenty, even in bright daylight.

Rate the light for durability:

Early days, but no issues.

Rate the light for weight:

Very light.

Rate the light for value:

You can get cheaper 100-lumen lights, but also more expensive units with lower outputs.

Tell us how the light performed overall when used for its designed purpose

The oval 30 LED arrangement really stands out and gets you noticed – especially in its 100-lumen mode. It doesn't blind you like some lights of this power output, which is great.

Tell us what you particularly liked about the light

The clip mount, which makes it really versatile (handy when you like to use more than one rear light when you ride).

Tell us what you particularly disliked about the light

The slight play in the rotating mount.

How does the price compare to that of similar products in the market, including ones recently tested on

The Giant Recon TL 100 has an almost identical weight, but costs £24.99 and trumps the Juno 100 for run-times. The Magicshine Seemee 100 is £25.99 and has a smart braking mode, while the Ravemen TR50 is £34.99.

Did you enjoy using the light? Yes

Would you consider buying the light? Yes

Would you recommend the light to a friend? Yes

Use this box to explain your overall score

It's very good: there are plenty of modes to choose from without it being confusing, it's simple to use and the run-times are good, if not quite as impressive as claimed. There are loads of mounting options too, making this a really appealing light.

Overall rating: 8/10

About the tester

Age: 39  Height: 6'4  Weight: 175lbs

I usually ride: Steel audax bike  My best bike is:

I've been riding for: 10-20 years  I ride: Every day  I would class myself as: Experienced

I regularly do the following types of riding: commuting, touring, club rides, sportives,

Add new comment


bigsy | 3 years ago
1 like

What an absolute con, this exact light is £5 on aliexpress

"the Juno 100 isn't bad value" really?

Hirsute replied to bigsy | 3 years ago

And how much for shipping, vat, customs duty though ?

2. Import duties, taxes and charges are not included in the item price or shipping charges. 

bigsy replied to Hirsute | 3 years ago

I'm sure I don't need to point out that it would be no where near £25

Hirsute replied to bigsy | 3 years ago

What will it be then  bearing in mind the current issues around import taxes?

RoubaixCube | 3 years ago
1 like

How much were the Jobsworth Dogstar Retena busters from PlanetX a while back?? £6-10???

Granted, they are discontinued on PlanetX but you can still buy them for a marked up price of £17 and they probably perform about the same.

(Ive noticed that some folk tend to buy up a lot of supply from PlanetX then sell them at marked up prices on ebay and amazon. This practise isnt limited to PlanetX either. I have come across people selling marked up aldi lights on ebay too)

Sriracha | 3 years ago
1 like

...the highest 100W flashing mode

Yikes! 100W from an LED. My back yard floodlight is less than a third of that, and it lights up the yard like daylight. 100 lumens, perhaps?

Truffl3Shuffl3 replied to Sriracha | 3 years ago
1 like

That's the special floodlight mode.

 I'll get that edited. Thanks for the spot!

Latest Comments