LWS Type Ram Blowout Preventers LWS Type Ram type BOP is lightweight Blowout Preventer designed for easy maintenance and long life. It is ideal for smaller bore and lower working pressure application. This field-proven Ram preventer has been the most popular Ram BOP in drilling and workover service for many decades. The LWS type BOP is available in either flanged or studded design. In particular, the studded top and bottom configuration is optimal on smaller rigs due to its compact design and reduced weight.