Futures 3.75 in. Alpha QD2 Quad Rear set.nDual fin set for rear fins of a quad surfboard setup.nFin system: Futures.nMade with an exclusive air and carbon infused composite.nBalanced construction that has enough spring to carve around sections, but also provides hold and stability.nFutures 3.75 in. Alpha QD2 Quad Rear set. Dual fin set for rear fins of a quad surfboard setup. Fin system: Futures. Made with an exclusive air and carbon infused composite. Balanced construction that has enough spring to carve around sections but also provides hold and stability. Made in USA. Vendor style #: 129332247. Fin specs: Size: Small (105-155 lbs). Quad rears: Base: 3.71 inches Depth: 3.76 inches Area: 10.73 inches Foil: Symmetrical. Construction: Carbon composite.