All Stainless heliarc welded construction for extra strength. 3-1/4" long by 1-1/2" wide, tapering to 5/8" at ends. Holes take # 10 flat head screws or bolts. Fin is 2-1/2" long & 1/8" thick with (2) 1/4" holes and (1) 3/8" hole. Complete with matching backing plate for through deck fastening on fiberglass boats.