This gudgeon is required to mount our Trucourse™ Rudder to kayaks with a flat stern without an existing mounting bracket. Great for mounting the Sea-Lect Designs Trucourse Rudder to most kayaks/boats without an existing mounting bracket, and a flat stern304 Stamped Stainless SteelA: 3/8" / B: 2-3/8" / C:11/16" / D: 1-11/16" / E: 2-1/8" / F: 1-3/4"