Parker Stainless Steel 316 1/4" Hex Head Plug with Buna N O-Ring, UNF Straight Thread, 3/8" Male Plug for closing and terminating the end of pipes or fittings Hexagonal head for simple installation and disassembly with a wrench Stainless steel 316 for strength and more corrosion resistance than stainless steel 304 Unified Fine (UNF) straight threads for increased strength O-ring for a tight seal