The TW Series is made for max stress for all your tough jobs. TW pressure pumps have a 24mm solid shaft for belt-drive, gear box, or flex couplers made for gas powered motors. Each pump has a. The TW Series pump features Die-Cast Aluminum Alloy crankcase that is not only made to protect against rust and corrosion, but is also oversized designed to dissipate heat and improves lubrication for a long life.