Made of Water resistant black phenolic plastic, has a 100,000 mechanical cycle life and 500 amp contact rating. Stinger's high current relays are the most efficient and reliable way to add secondary batteries to your system. This new for 2011 item has the highest current handling capability to date. Simply connect these relays to operate when the ignition is turned on. The battery system will remain separate while the ignition is off, preventing system drain. Compatible with all types of alternators and charging systems.