The Keystone K-LOK Series 36/37 is a high-performance butterfly valve rated to ASME Class 150 and 300, available in wafer, lugged and flanged style. The unique design has bi-directional sealing for various pressures, as well as dirty services. It ensures safety, minimal leakage, and extended life. The K-LOK polymer and elastomer seats provide bi-directional, drop-tight shut-off in vacuum as well as at full rated differential pressure. The blow-out resistant shaft is standard on all valves for increased safety. A unique packing design allows for use in pressure as well as vacuum without modification or special assembly.