Reelight Rl721 bike lights are a set of front and rear bike lights. They are always on because they are powered by your bike’s movement. Put them on your bike and never be without bike lights again.
Reelight Rl721 Bike Lights – Lights that are ALWAYS ON
I have lights on the front and back of my helmet, as well as on the front and back on my bike. I use rechargeable batteries, and I’m pretty good about switching them regularly.
Still, I’m not perfect, and I wanted to make sure I was never caught coming home from work without lights. That’s why I bought a complete set of Reelight Rl721 bike lights.
Reelights are Powered by Electrodynamic Induction

The Reelight Rl721 bike lights are powered by electrodynamic induction, which means that power is generated as your bike moves. This is thanks to a pair of spoke-mounted magnets passing over a copper coil (inside the light unit). Once you have them mounted, they are always on. You don’t have to remember to keep the batteries charged, or even to switch the lights on. As long as you’re moving, your Reelight Rl721 bike lights are on.
Note that the lights will not work at full capacity when you first get them, as it takes a while to get the capacitor charged up. After this first time use, however, they are up to speed within a couple of minutes of starting your bike journey.
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Legal Issues and Reelight Rl721 Bike Lights

These lights were invented in Denmark, where there is a legal requirement to have lights on the back and front of your bike. They meet the legal requirements of most countries, and even offer a left side driving option. A few countries (such as Holland and Sweden) have laws against flashing lights, so Reelight offers models with a steady light (the SL150 series). These are handy if you don’t want to annoy people with flashing lights.
Related Post: When to Use Flashing Bike Lights
Some claim that because these lights attach to the bike’s axles, they are too low to meet the legal requirements of some countries. I am not sure about that. However for me it is a moot point, because I would not use these lights as stand-alones. I use them as extra or back-up lights.
My primary taillight is my intensely bright Serfas taillight (reviewed here). I love that I can easily and quickly move this light to a different bike.

My primary bike head light is my wonderfully bright Lumintrail headlight (reviewed here). I love that I can mount this on my helmet, so I can easily direct the light where I need it.
Fitting your Reelight Rl721 Bike Lights
The compact Reelights Rl721 Bike Lights will fit most bikes. Reelight recommends that there should be no more than 3 mm between the magnet and the light. Mine were poorly fitted by my bike shop, with the front set touching and the rear set more than 3 mm apart.
I had to adjust them to get them working perfectly, but it really was not brain surgery. The kits ship with all the accessories you need to mount them.

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Bottom Line on Reelight Rl721 Bike Lights
What I Like about my Reelight Rl721 Bike Lights
First off, I don’t have to worry about batteries. Which also of course makes them really green friendly – always a great thing. However, for me the greatest benefit of the Reelight Rl721 lights is simply that my lights are always on, even when it suddenly gets darker, or the batteries on my other bike lights run down.
This could potentially save my life. I know a woman who was hit head-on by a car while she was cycling after dark, because she did not realize that her front light battery was completely dead. (Luckily, she survived.)
Plus, my Reelights are on during the day as well. I once spoke with a bus driver who told me he prefers cyclist to have lights on even in the daytime, as he can see them from two blocks away (but he finds it hard to see them at all without lights).
Bearing this out is a study conducted by Reelight and other researchers with 4,000 cyclists over one year. This study showed daytime lights on bikes reduced accidents by 19%, and reduced injuries to cyclists by a staggering 47%. (Thanks to Canadian safety activist and academic Neil Aronson for drawing my attention to this study.)
Related Post: Best Bike Light under $40 – Serfas Thunderbolt Tail Light Review
Bottom Line on Reelight Rl721 Bike Lights
These lights are not stand-alones – you still need your regular bike lights for biking at night, especially on the front, as they do not light up the road ahead of you. Reelight Rl721 bike lights are more about being seen by others, than about seeing. So I definitely see my Reelight Rl721 bike lights as back-up lights. They make sure I will never be caught lightless, but I would not want to have them as my only lights.
Some people might have a problem with the weight of these lights, as they are pretty solid. I laugh at such notions, seeing that I can lose or gain four pounds in a single day without even thinking about it. (Actually, I am much better at GAINING four pounds in a day without even thinking about it. My Super Power is gaining weight. No, not the power that I would have chosen …)
For me, on my sturdy commuter, a few ounces more or less is not even worth thinking about.
Related Post: Complete Guide to Bike Lights
Reelight Rl721 are always there and always on, with no running costs. So even if they save my life only once, it’ll be money very well spent. My opinion is that it’s well worth while to shell out a few of your hard-earned dollars on these clever and possibly life-saving bike lights. You can have the whole set with all accessories shipped from Amazon for about $65.
More About Bike Lights
To read much more about bike lights, see our Average Joe Cyclist Guide to Bike Lights. If you want a light that will enable you to see your way in pitch darkness, see my review on the super bright Lumintrail headlight.
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