Constructed of fiberglass filled injection molded nylon. Contain no metal and do not require grounding. Caps are color-coded for easy deck fill identification. 1-1/4" ? 11-1/2 NPSM straight cap threads. Installs with three #10 FH fasteners (not included). Type Gas Cap Color Red A 1-1/2" B 2-1/2" C 3-3/8"