These #28 O-ring joint pinch clamps are used with our Ideal Vacuum Glass Manifold, U-tubes and attachments. They have a screw type locking device and are used for 12 or 15 mm inner diameter O-ring joints or 28 mm spherical ball joints. They are an easy way way to attach and detach multiple sections of glass, O-ring joints, or spherical ball joints. Requires a #116 O-ring for seal. Made of stainless steel.