You just set up your equipment for the first dive of your vacation in Saint Somewhere, you start to test the function of your battery operated gear and either your computer won't, your camera's flash, film advance or LCD won't function. The worst thing that can happen on a tropical vacation has just happen No Dive Computer or Camera. Don't leave on a vacation without spare batteries why ruin a great holiday because of a few dollars in batteries. Always pack some spares, don't forget your Dive Light needs some too! These CR123A 3.0 Volt Lithium Batteries fit many dive computers, dive lights, cameras and other electronic devices. Don't pay Island prices. Batteries are a great save-a-dive-kit item.