Extremely powerful tail light with STVZO optimized lens and two ultra bright LEDs provide class leading brightness. Lightweight, durable construction is waterproof and provides side visibility for added safety. There are two power modes to choose from: 35 lumen Blast Mode runs 1.5 hours and 15 lumen Economy Mode runs 4.5 hours. Mode Memory feature returns to the selected mode when the light is turned on. An integrated USB stick provides convenient cable free battery charging and a rugged, versatile seat post strap securely mounts to a wide variety of round and aero posts.