Shortboard tri-fins usually have a 3.5-4.5 inch base, longboard single fins are about 6 half inch. They are primarily made of fiberglass and will be more expensive than foamies and pop outs. Surfing boards have foam in the center that is protected by either epoxy or fiberglass. http://Mxdeloitte.biz/__media__/js/netsoltrademark.php?d=Jayhagan.com%2F__media__%2Fjs%2Fnetsoltrademark.php%3Fd%3DYas55.com%252Fcomponent%252Fk2%252Fitemlist%252Fuser%252F4740023.html