Portland Design Works Gravity+ 100 USB Rechargeable Taillight. The Gravity Tail Light has a built in accelerometer that detects deceleration or swerving and automatically changes to a super bright solid beam to warn following traffic.
Automatic accelerometer brake light function shines 100 lumens bright
2 Modes (runtime): Solid - 20 lumens (12 hours) Flash - 80 lumens (30 hours)
USB rechargeable li-polymer battery
Includes brackets for seatpost and seatstay mounting