The Marwin seat rings are encapsulated in precision-machined metal recesses which are, in turn, machined into the valve. The encapsulated seat protects the seat against line flow, resists seat distortions during modulating conditions, and has tight compartment sealing. This feature creates an ideal valve for modulating by supporting the seat rings during opening and closing operations. The 3000 and 10000 Series three-piece ball valves are available in a wide spectrum of materials from the standard body materials to the specialty alloys such as Monel, Hastelloy, Duplex, 254-SMO, and Alloy 20. Marwin Ball Valves, 3170 Wasson Rd., Cincinnati, OH 45209. Tel. (800) 628-2583, fax (513) 533-7343.