Single FinAll HUDSON Fins are hard anodised aluminium for maximum durability and corrosion resistance. The Single Fin is offered in both Breakaway and Classic style. The Breakaway style was introduced in mid 2005 to allow for a quick onsite replacement option, and can be used on any HUDSON Single with a set screw at the bow end of the fin box. The Coastal fin is suitable for all O3. 31 Coastal Singles. Find our fin installation guide here.