4" Tri Clamp WyeTri Clamp Wyes offer an evenly divided bi directional splitter, or dual flow combiner. DETERMINING TRI CLAMP SIZE Tri Clamp sizes are determined by the outer diameter of the pipe or tubing, not the outer diameter of the flange or Tri Clamp itself. The flange of a Tri Clamp fitting typically has about a inch greater diameter than the outside diameter of the pipe. This can become especially confusing when the Tri Clamp fitting has no pipe attached to