This 6 in. x 6 in. adapter plate has a 1-1/2 in. threaded coupling for national tapered pipe. It is used in conjunction with one of our 1-1/2 in. single-pipe adjustable-height suspension adapters (ASA-2446 or AST-2446) for drop distances of more than 3 ft. 10 in. Pipe coupling is slotted for safely routing signal cable through pipe interior.