An extended housing shields the terminals on these relays from weather. They're also rated IP54—when they're plugged into the relay socket, they're sealed to keep splashing water, like rain, from getting inside. They handle high starting (inrush) currents that often occur when turning on a vehicle. To prevent damage to sensitive equipment, these relays will partially suppress a momentary surge in voltage when the relay switches off. They’ll take a voltage spike of 300V to 500V and bring it down to 100V.

Relays for surface mounting have a tab for added security in high-vibration applications.