This product is used to test the largest amount of current each of the fuse can receive. There are 5 types of fuse for this testing which are 0.5, 1.0, 3.0, 5.0, and 10A. There is a mechanic that conducts the amount of amperes sending to each of the fuse, and the type of fuse used. There is a button which is used to test the amount of current sent to each fuse. Directions of usage can be seen on the wooden base. This product uses current 6-12V A.C