With the Eternal Tools & Home Improvement Universal Battery Tester and Organizer you determine where the battery is on its predictable life curve, you know when to replace a battery and locate weak cells . PORTABLE & EASY TO USE - This lightweight battery tester is compact and fits easily in desk drawers. The slider adjusts to fit multiple battery sizes. ADAPTABLE - This universal battery tester works with both standard and rechargeable household batteries and can test many different types of batteries. Works with any 1.5v batteries, button cells, and 9v batteries. TEST ANY BATTERY TYPE -This universal battery checker can be used for alkaline batteries, dry cell, or rechargeable batteries. TEST ALL BATTERY SIZES -Check AAA, AA, C, D, 9V and 1.5v button batteries into the battery tester and instantly find out which ones are good.