This item is a button cell power tester checker, can adjust to three kind of battery :7mm,10mm,20mm seperately. Place cell battery into the concave and check the pointer, moves slightly to accommodate the battery to make sure the positive and negative terminals is in good contact. A great gadget for instant testing of your battery capacity, can check button cell battery& 39;s power. Features - Color: mainly green. - Material: plastic. - Size: approx. 9.9* 5.4* 2.8cm. - Power source 6F22(9v)xl (not included). - universal button cell battery tester. - A great gadget for instant testing of your battery capacity, can check button cell battery& 39;s power. - Adjust to three kind of battery :7mm,10mm,20mm seperately. - Place cell battery into the concave and check the pointer. - Moves slightly to accommodate the battery to make sure the positive and negative terminals is in good contact. - Note: The battery checker is only for Button Cell. Operation Manual(three different zone) - When the indicator is on red zone, the battery is low power station and must be replaced. - When the indicator is on yellow zone, the battery is current. - When the indicator is on green zone, the baterry is full.