... 3.Seat : EPDM , PTFE , NBR , VITON . 4.Stem : Carbon Steel , Stainless SteelDesign standard: API609 , BS5155 , MSS-67-1995Face to face : API598Tubing ... butterfly valve .5. 5.Butterfly valve and check valve of Stainless - with lever , ball valve with electronic apparatus .6. Y ... resistant butterfly valve.etc. handle lever soft-sealed carbon steel or stainless steel high-performance butterfly valve