Engine braking is a powerful and important technique that all bike riders use.
The trouble with engine braking is that it does not illuminate the brake light.
Problem Solved with Hands-Free Rear Light
Hands-Free Rear Light is controlled by your smartphone.
Upon engine braking, Hands-Free Rear Light senses slowing down and (automatically) activates the brake light.
Your bike is now visible upon engine braking.
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