This is a 6 volt, 4 amp-hour rechargeable replacement battery made for Ultratec lights. The supplier lists it for the Ultratec MS1081, MS5151 and MS5171 models, rechargeable lamps whose internal battery eventually loses capacity after years of charging. Fitting a fresh battery restores the runtime of the light at a fraction of the cost of a new unit. Before ordering, check that the voltage, capacity, size and terminals match the battery in your lamp, and dispose of the old battery at a proper recycling point rather than in household waste.