Channel Islands Britt Merrick Twin Fin Britt Merrick’s hand foiled signature twin fin set is designed to fit between a traditional upright and keel fin. While conceived to maximize the performance and flow of the new CI Twin Pin, the setup works great in any twin fin board when you are looking for the perfect combination of drive, hold, and release. Dimensions: Depth | 5.31" Base | 5.77 ” Area | 23.58 sq in