Overview: This product is a 2-ch relay expansion board, suitable for Raspberry Pi Zero/Zero W/Zero WH/2B/3B/3B+/4B?STM32?Arduino etc, two relays on board, can control shutdown independently. Specifications: Size: 56mm(Length)*34mm(width) Optocoupler: LTV-357T-B-IN Supply voltage: 3.3V&5V Package contents: 1. 2-CH Relay HAT *1 2. Copper column * 4 3. Screw * 4 4. PH2.0 to DuPont bus head line * 1 5. PH2.0 cable at both ends * 1