Diodes are used to tie into the towed vehicles's brake light, running light and turn signal wiring, and connect it to the motorhome. Diodes permit electrical current to flow in only one direction — from the motorhome to the car — preventing electrical feedback and the damage it can cause to the towed vehicle's dashboard electronics. If you’re using a diode, why not use the best? ROADMASTER’s Hy-Power diodes have a heavy-duty, anodized aluminum heat sink, and each diode is protected against the elements — all components are housed inside an epoxy-sealed, anodized aluminum case. Four-pack required for most vehicles. Includes detailed wiring instructions.