First revision trackpad battery cap, Second revision aluminium bluetooth keyboard battery cap. This is the cap that screws into the battery compartment to keep the batteries in place on the A1314 2009 and 2011 models of wireless (Bluetooth) aluminium keyboards which took two batteries. This cap will not fit the original A1255 models which took 3 AA batteries. The screw end has a machine finish. This cap is approx. 6mm deep and much shallower than the original version.