This is a 5V 8-Channel Relay module, it allows the Arduino to control high power sources (see ratings below).

• 8 Relays on board
• Normally Open (NO) or Normally Closed (NC) operation
• Each 5V Relay requires 20mA driving current
• 5V 5mA TTL control input which can be directly controlled by Arduino, AVR, PIC, ARM and others.
• Indication LED for each Relay's Status
• Relays are rated at 10A@250VAC and 10A@30VDC
• Size: 13.4x5.3x1.7cm / 5.28x2.09x0.67in
• Weight: 116g / 4.11oz