Best used as a replacement rudder gudgeon for Mission brand kayaks outfitted with the OrigiNZ Rudder. Accepts a 1/2 inch diameter pin (about 2 inches long) Comes with a cotter pin that secures the rudder pin (a 2nd part secures this black plastic receiver to the hull of the kayak). This receiver gudgeon is approximately 2 1/2 inches long, 1 1/16 inches in diameter at the top and 3/4 inches at the bottom. The hair clip cotter pin is made if wire about 1/8 inch diameter, bent to about 2 1/4 inches in total length.