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Moon Gemini Rear Light



Perfect for day-time and street-lit commuting or as a secondary/back-up option

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.

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Moon's Gemini is a featherweight USB rechargeable rear light that clips on easily and is bright enough for urban commuting. The small single button is surprisingly easy to find in big gloves.

The Gemini is a new addition to Moon's Tail Light range and benefits from many of the features of its more expensive big brothers. It has a spot angle of 95 degrees at 10 metres, giving an effective span of 22m. The total angle is helped by the two single LEDs, resulting in a full 360 degrees, very useful for urban riding. The brightest 20-lumen constant is also perfect for partially lit commutes; I prefer a slightly brighter rear for my unlit rides, but this also works well here as a backup or secondary light.

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The Gemini clipped easily onto my seatpost and I quickly toggled through the seven modes to find the 'day flash' setting, perfect for even a bright, sunny morning ride to work. While it's currently still daylight for my commute, I've only really needed this day flash mode; it gives a sharp 30-lumen flash, with a quoted 30-hour run time from its rechargeable lithium polymer battery (3.7V 300 mAh).

The run times are pretty much spot on; having left my light on in the shed overnight, I was surprised to find it still flashing the next afternoon. As with any light, a constant beam does run down the battery at a much faster rate – 1:40 (claimed) when running the light's brightest constant 20-lumen setting; my light lasted 1:44 on the same setting from a full charge. This is still more than enough for most commutes, at least one-way, so you could charge it during your working day if you have that option, ready for the ride home. Charge time is only 2 hours from flat, a little longer if charging from a laptop.

Connecting the light to your bike couldn't be simpler thanks to Moon's universal mounting bracket. The RB-22 is compatible with all of Moon's lights, so switching this out for something bigger is easy. The catch feels sturdy and I've had no worries about the light bouncing out on rough terrain. I tested my theory on a cyclo-cross ride and it stayed put. Top marks!

> Check out our guide to the best reflective clothing and accessories

Build quality is really rather good too, with no part of the light or its mounting bracket feeling poorly made. The CNC aluminium heat sink casing means bashes shouldn't ruin your light.

I was initially concerned by the single button on the rear of the light – small buttons are usually difficult to find in thick gloves – but the rubberised material and its protrusion from the light body meant I had no problems. The button also makes a positive click that helps when trying to cycle through settings on the move.

Overall, this is a great little light to help make sure you're seen during the day and under streetlights, or as a secondary light in the dark.


Perfect for day-time and street-lit commuting or as a secondary/back-up option

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Make and model: Moon Gemini Rear Light

Size tested: n/a

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?

A small unit designed to be a secondary light for night riding or a primary light for day time commuting/riding.

Raleigh (distributor) says: "Gemini provides exceptional additional visibility for your person or bike. The 2 independent high brightness LEDs can be constant, flashing or chase modes"

From Moon:

USB rechargeable light

360 degrees Total Angle

95 degrees Spot Angle

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

From Moon:


2 pcs high brightness red LED

CNC Aluminium heat sink casing

Auto safe mode

Mode memory function

Rechargeable lithium polymer battery (3.7V 300 mAh)

7 modes: Mode1 / Mode2 / Mode3 / FL 1 / FL 2 / ALT FL / DAY FLASH (DOUBLE BLAST)

Quick release universal bracket RB-22 (fits all round bars and AERO style bars)

Low battery, charging and fully charged indicator

Automatic fully charged cut-off system

Side visibility

Water resistant (IPX 4)

Rate the light for quality of construction:

The CNC aluminium heat sink casing gives this small light a very robust feel. The small button is easy to use in thick gloves and has a positive click.

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

One button controls all the settings. You can also fit the light in a rush to get to the cafe. Superb.

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

The O-ring holds this securely in place and the bonus of having a universal mount is that you can switch in a bigger light for dark country lane commuting.

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

After drowning it with a hose there were no problems or any sign or water ingress.

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

The brightest 20-lumen continuous setting drains the light rather quickly, 1hr 44mins (1:40 claimed). But recharging is fast and lower brightness settings last for ages.

Rate the light for performance:

Clip it on. Click it on and go.

Rate the light for durability:

I soaked it with a hosepipe and then accidentally left it out in the rain overnight. No water ingress, and the light is still working perfectly.

Rate the light for weight:

Will you notice 28 grams? I forgot mine was on the bike.

Rate the light for value:

On par with its rivals.

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

Better than I expected. The button is the big thing here. Being able to operate such a small button in bulky gloves is brilliant.

Tell us what you particularly liked about the light

The memory function – so once I'd found the setting I liked, it would turn on to that automatically.

Tell us what you particularly disliked about the light


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 score

It's well made and just works very well, without any fuss.

Overall rating: 8/10

About the tester

Age: 22  Height: 1.77m  Weight: 61kg

I usually ride: Rose Xeon RS  My best bike is:

I've been riding for: 5-10 years  I ride: Every day  I would class myself as: Expert

I regularly do the following types of riding: road racing, time trialling, cyclo-cross, commuting, club rides, general fitness riding, I specialise in the Cafe Ride!

Add new comment


zero_trooper | 2 years ago

I'm posting this here as in another thread, which I now can't find  3

Someone was wanting suggestions for a small rear light. I commented that I really liked my Gemini, but it had randomly failed after about three years use.

Well I've done the resurrection shuffle and managed to get it working again   1

However, possibly down to user error! MOON hasn't the most straightforward operating sequence (check out reviews for the Sirrus PRO) and I've probably just forgotten how to switch it on <facepalm>

Having said all that, still love my Gemini and glad it's now working:)


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