Attwood Wedge 2 Inch Extension Post Type B seat mounts are designed to "lock" into the post. Engineered to prevent unintentional detachment Heavy-duty bushing with peripheral bearing system and exclusive "crush ribs" are individually sized for exact fit Tubing is precisely-sized and satin-anodized finished. Bead blasting closes aluminum porosity. Brushing process provides long-lasting high-sheen finish Tubing comes in several styles. Pedestals come in several lengths, including patented "J-Slot "adjustable height. Strong base design has reinforcing ribs and improved profile to withstand the toughest conditions Precisely positioned locking tab positively locks post to base. Wedge bushing locks in with a tight, solid fit. 2-Point stainless steel riveting strengthens the bushing.