CPR Aquatic BHCPR100TTx4 1" Thread x Thread ABS Bulkheads (Set of 4) Pack of 4 complete units 1" High Quality ABS Bulkhead with a silicone washer and dome top for better structural integrity Thread x Thread (flange x stem) Fits standard schedule 40 or 80 PVC pipe & 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