Molded to the highest standards using top quality UV stabilizers and antioxidants. When installing, use silicone sealant on hull or deck surface. Lubricate with Vaseline or Teflon grease. Installs with six #8 FH fasteners (not included). Avoid contact with acetone or strong solvents. ID 4-7/16" OD 5-3/4" Color White Cut Out 4-1/2"