There are 4 fixing screw holes around the board, with a hole diameter of 3.1mm, making it easy to install and fix. The relay uses high-quality relay, single pole double throw. A common terminal, a normally open terminal, and a normally closed terminal Low level pull-in, high level release. The status indicator light is on when it is engaged and off when it is released. Relay maximum output: DC 30V/10A, AC 250V/10A Wiring instructions: VCC: system power positive pole GND: negative pole of system power supply IN1--IN8: relay control port Colour:Photo Color Material:plastic Package Contents: 1 x Relay module Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.