Standard 1 1/8 inch plug with PRD integrated for the end of a cylinder.
Port size is -8 F BSPP, fitting not included, but can be requested. -8M BSPP x -8 (3/4")M ORFS for flanged tubing/hose adaptation or 1/2" Compression x -8M BSPP for connecting to a stainless steel vent line. 1/2" or -8 is the required minimum for a vent line according to NFPA 52.