Sigma D-PWP-C4 4" PV-LOK Domestic Serrated Bell Joint Restraint incorporates a series of machined serrations that effectively engage the PVC pipe walls to provide positive joint security and full support of the pipe. The series D-PWP incorporates two PV-LOK clamping rings and a series of restraining rods & nuts that tie the two rings together and secure the PVC bell and spigot pipe joint.