Attwood Clamp-On Boat Seat Swivel Mount - Black powder coated helps these seat mounts last almost endlessly as they are moved around and removed from a boat bench or other application. These clamp-on boat seats are great for jon boats and other small fishing vessels to add a swivel and boat seat with a back on it. Clamp-on swivel mount; Black powder coated; Fits most seat hole patterns; Adjusts from 7 1/2in to 18in;