These board rack mounts are machined from aerospace-grade billet aluminum and are anodized and electropolished to give you years of maintenance-free use. Designed specifically to mount the PTM Edge CBR-100, CBR-200, and BBR-200 Clamping Board Racks or the PTM Edge BBR-100 Bungee Board Racks to a 1.2″-square 4-bolt pattern. (Fits most Nautique towers.)