Profile: Westrex Corp. specializes in vacuum tube production. We offer professional, telephony and military products. Our western electric™ 300B vacuum tube is a vacuum tube. These are available in single or matched pairs with octets and are available in all major forms. These vacuum tubes provide medium, four-pin thrust type bases used in western electric 143B or similar sockets. The 300B tube has the bayonet pin that may also be mounted in a western electric 1OOM, 115B or similar socket. The tubes may be mounted in either a vertical or horizontal position.