All thermoplastic [PVC, CPVC (Corzan), Natural unpigmented Polypropylene, Glass-filled Polypropylene, or PVDF (Kynar)] chemical gauge guards are to be of two piece construction (upper and lower housing) with a one piece flexible [PTFE (standard for pressures above 15 PSI), EPDM, or Viton (EPDM and Viton are to be used for vacuum and pressures under 15 PSI) ] diaphragm between them as a barrier seal. The upper and lower housing are to be joined using six (6) stainless steel assembly screws to effect a uniform, secure and vibration free sealed assembly. All units are to have a 1/2" NPT process connection and a 316 stainless steel hex insert, to prevent over-tightening, 1/4" NPT instrument or gauge connection as standard. Sealing at the 1/4" NPT instrument or gauge connection is to be accomplished via an elastomer O-ring seal at the base of the threads in the hex insert to avoid cracking due to over-tightening of the metal instrument/gauge. All units are to be 100% individually tested at the factory. As manufactured by Plast-O-Matic Valves, Inc., Cedar Grove, NJ.