Every home should have this unique electrical accessory on hand because itís so versatile. Tests all AAA, AA, C, D, 9v and button batteries, whether general-purpose, alkaline or rechargeable. Portable battery, bulb & fuse tester is handy to have at home or the office. Simulated load test to check if battery will work in use. Use it to test all standard household and auto light bulbs, and fuses too. Dual scale allows testing and measuring battery voltage or capacity. Requires one 9v battery (not included).