Despite its light and compact design, this device uses a flashing light (strobe) to signal a diver's location up to 2km away on the water's surface. It can operate for 10 hours on two AA alkaline batteries. It also includes a light that reaches up to 100m. Product Details Specifications: 100m pressure resistance, uses 2 AA batteries (sold separately) for 10 hours of use Color: Orange Size (cm): Diameter 4.7 x Length 13.6 Weight: Approximately 112g Manufacturer: BBC Used approximately 150 times. After each use, it was rinsed with fresh water, and the O-rings were re-lubricated with silicone oil before being stored in a closet. I have tested it with batteries and confirmed that it is working without any problems. This is a used item, so please consider purchasing only if you understand this.