Allen - Bradley 1719 - ARM is an empty slot cover of the 1719 Ex I/O series. Here are its brief parameters:
Pin Number: 8 pins
Approximate Mass: 65 grams
Dimensions: 16 x 100 x 103 millimeters
Function: It is used to cover the empty slots on the backplane when needed, and can also fix the unused field - wiring. It does not retain an address and can be placed in any order on the rack.