Cherne Gripper series end-of-pipe (inside pipe) mechanical plug seals the end 3" DWV pipe for Drain/Waste/Vent and/or stack testing. Simply position the plug inside the pipe and rotate the metal wing nut to expand the rubber gasket. Universally compatible with all DWV (Drain, Waste, Vent) pipes - including Sch 40/80 PVC, ABS, cast iron (no-hub, service weight and extra-heavy) and others. Note: for use inside pipe only, not for use inside the fitting (hub portion). Max. back pressure is 17 psi / 40 ft of head.