We are offering center disc lug type butterfly valve. design feature the unique center line seat and disc design insures positive valve sealing while maintaining low seating torque.all center line butterfly valve discs are precision machined to a half ball profile, providing a precise disc to seat relationship.center lines cartridge style seat incorporates an elastomeric bonded to a phenol stabilizing ring, eliminating elastomeric movement and reducing seat tearing or fatiguing due to bunching.center lines basic three bushing design completely isolates the valve shaft from the body, resulting in increased control of the valve disc, lower valve seating torque, and longer valve life.the center line cartridge seat has a much smaller mass of elastomeric than traditional boot seat designs, limiting seat swell and the accompanying variations in seating torque.