Heavy duty relay, capacity 40A. This relay is sealed from the elements. The size is approximately 1 x 1 x 1 inch cube, with a mounting tab.
If used in a wet location use dielectric grease on the terminals. 40 Amps is a substantial amount of power, approximately eight 55watt headlights. This relay is rated to switch 40A, 100,000 times!
The terminals are numbered, and the wiring diagram is molded into the side of the unit. See the "Larger Image".