attwood Wall-I Swivel Seat Mount Cast aluminum 3 degree tilt 3 inches required diameter mounting holes Wedge-shaped components slide in for a snug, Stable fit Engineered for a wedge-tight fit Type B seat mounts are designed to "lock" into the post Engineered to prevent unintentional detachment Heavy-duty busign with peripheral bearing system and exclusive "crush ribs" are individually sized for exact fit