This unit is designed for 5″ diameter poles and is used with rope style internal halyard systems. Each unit consists of a hinged door mounted to the front of the frame and a cam cleat (optional) mounted to the back of the frame. The entire unit is inserted into the flagpole shaft and secured with eight 1/4″-20NC stainless steel screws. Minimum hole opening 5-1/2″ x 3-1/4″. Lock & keys included.