acr 3959 C-Strobe Life Jacket Emergency Light Intense strobe light visible up to 2 miles (3.2 km) Waterproof and corrosion resistant case More than 8 hours continuous operation Uses two -InchAA-Inch batteries One year warranty Intense strobe light visible up to 2 miles (3.2 km) Comes with steel clip and adjustable Velcro strap; can be mounted on bicycle frame, pole, etc. Waterproof and corrosion resistant case New attachment pin engages top cap; prevents accidental disassembly Weight: 2.6 oz (74 g). Size: 6 x 1.6 in (15.3 x 4 cm)