This bushing adapter has a male Ace-Thred connection at bottom and a female NPT thread drilled into the center of the top of the bushing. The top FNPT connection matches male Swagelok fittings and facilitates joining plastic or metal tubing to Ace-Thred glass fittings and adapters. This adapter is supplied with one FETFE o-ring (-176 does NOT come with o-ring). Adapter is available in nylon, HDPE (High Density Polyethylene), or PTFE. -120 and -125 are PTFE, MNPT to FNPT connectors.