Matthew C.wrote a review of Portland Design Works Gravity Plus USB Tail Light on January 30, 2019
Familiarity: I've used it once or twice and have initial impressions
The light worked as advertised, however it fell off on the 2nd ride never to be seen again. The strap was still attached but the light came off at some point and it seems to be a poor quality on the attachment design. Not worth $40 for 1 ride.