This style diaphragm is the same as the Type F in all respects except flange mounting. The parts are moulded with what equates to half of an O-ring on the flange rather than a large flat surface. This O-Ring half fits into a groove machined into the cylinder half of the hardware. Sealing is achieved by squeezing the bead into a properly sized groove (see table at bottom of page). The cylinder and bonnet can then be designed to make positive contact when assembled, eliminating the need for a closely controlled assembly torque. It also reduces the overall diameter of the diaphragm, reducing the hardware diameter.