CatEye's TL-LD130 Taillight features 3 ultra-bright LEDs for excellent visibility, flashing and steady modes, and runs for up to 150 hours on the included 2 AAA batteries. Plus, it includes a no-tools universal mount and a clothing/bag clip, too.
Run time in hours: 75, 150, 150 (constant, flashing, random flashing)
Weight in grams: 48
Batteries: 2 AAA (included)