CPR Aquatic 2 Count Slip by Thread ABS Bulkheads for Aquarium Filters, 1.25-Inch Pack of 2 complete units 1-1/4" ABS Bulkhead - Hard to Find Size Slip x Thread (FPT) - (flange x stem) Fits standard schedule 40 or 80 PVC pipe and fittings; Nominal Pipe Size and Standard Pipe Thread apply to inside; outside threads are not standard PT Look for the CPR UPC label. Don't accept imitations