The SitePro 4364 is designed to provide non-slip grip while preventing user to over-tightening clamp and crushing the prism pole. Used by a surveyor to set up a freestanding GPS antenna pole or prism pole. Fits 1 to 1.25 inch (25.4 to 32 mm) outside diameter poles easily through the open-face head with anti-crush clamp. 1.5-inch (38 mm) poles be attached easily through the top of the open face clamp