Isomat Plastic Snap-in Halyard Exit Plates are molded in Black Plastic and "snap" into place. Unit measures (visible when installed) 4 1/2" long x 1 5/16" wide (115 x 34mm), and fits in mast cut-out 112mm long x 26mm wide (4 1/4" x 1"). Suitable for use with line up to 5/8" (16mm) diameter.