Modern Headlights

Good, but the relays themselves don't get the whole job done. There's still the too-thin power and ground wires to the lamps to consider, and headlight sockets available from the parts store have the same pathetic 18ga wire on them. Hence parts kits that contain the relays, the terminals, the plugs, the sockets, the fuses and fuse holders, etc. so you can do it up right.