This is an input/output simulation board used for testing programs in small SBC like Arduino and Raspberry Pi or industrial PLCs. It has terminal blocks for easy wiring. There are 8 push buttons that can be wired for negative common or positive common. The 8 LEDs are two color, Red and Green. When the output common is negative and positive is switched to the LED it will be Green. When the output common is positive and negative is switched to the LED it will be Red. There are 12mm tall standoffs that snap into the board. The back side is threaded 2.5mm for mounting to a surface. The dimensions are 2.75" wide x 4" long x 1" tall when assembled. The quantity provided is 1 board with 4 standoffs. Operates on 18vdc ~ 24vdc.