3/4" Pex x 3/4" Female Pit Thread, Swivel Coupling, Connects 3/4" Pex Or Polybutylene & 3/4" Male Threads, When Connecting 3/4" Polybutylene With This Fitting Always Use Part # 06792, 3/4" Pex To Polybutylene Transition Insert, Wall Of 3/4' Polybutylene Is Thinner Than Pex & Requires This Insert To Ensure A Complete Seal.