Constructed with UV stabilized injection molded ABS and feature a clear polycarbonate lid. 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 solvent. ID 4-7/16" Color Black Center Clear Cut Out 4-1/2"