An isolator is used to combine two batteries when an alternator is charging (engine running) and isolate them when they are not charging (engine off) so you can still start your vehicle. Connect the two small studs to each other to ground and the other to an ignition source from the fuse box, the order on the large/small studs does not matter 2 copper tips, housing, galvanized steel housing/plate holder. Voltage: 24V Color: silver Material: metal Size: 85.3 x 67.4 mm Package Contents: 1 x Starter Relay Only the above package content, other products are not included. Note: Light shooting and different displays may cause the color of the item in the picture a little different from the real thing. the real thing. The measurement allowed error is +/- 1-3 cm.