This buttress adapter has a 63mm opening. It fits Russell-Stanley®, Sonoco®, Greif®, and most other US-made plastic drums. No need to "make do" when using standard 2" NPT threaded pumps and faucets and other equipment in plastic drums with buttress thread bung openings. This precision-molded high-density polyethylene adapter will do the job right. Green in color. This adapter has a male buttress thread to thread into the buttress thread on a drum. It adapts the buttress thread to a 2" female NPT thread.