The Allen-Bradley / Rockwell Automation 1771-A4B I/O Chassis is for the 1771- I/O modules. 1771A4B houses 16 slots. Approximate dimensions are 315 x 610 x 193mm (12.4 x 24.0 x 7.6in.). Approximate weight is 6.7 kg (14.8lbs). The I/O Chassis mounting type is a back-panel mount.