Types of Fins

There are three main types of surf fins:
Soft (Flexible) Fins
Soft (aka flexible) fins are used on many rental boards to avoid injury liability. They are, of course, safer than a hard fin but there is a sacrifice in performance.
Glass on Fins
Permanently adhered classic glass on fins are attached to the surfboard by laid on  fiberglass. This was the method of choice for old school surfboards before the advent of the fin box. That technology advance made glass on fins mostly obsolete because they  are damaged easily and require now rare expertise to repair.
Removable Fins
Fin Systems that use a fin box are the most popular option today. Removable fins are can be unscrewed from the surfboard and replaced by various fin designs or even be relocated on the board to vary setups to customize, experiment and tweak your board's maneuverability, stability and speed.