I'm not kidding about the price. Those Hyperlite shelters? $500 and up. The Mojo UFO? A wallet-splitting $1,799. The stuff sacks from Zpacks are your most reasonable option for getting your hands on this space-age material. A 0.3-ounce medium stuff sack will run you only $15.95.
Medium cuben fiber stuff sack
Produced and marketed by the Cubic Tech Corporation in its CTF3 product line, cuben fiber is a non-woven fabric that sandwiches Dyneema fibers between two layers of composite laminate material. (With a strength up to 15 times that of steel, Dyneema is dubbed "the world's strongest fiber.") The resulting fabric is extremely strong, waterproof, and highly tear-resistant.
Cuben fiber first appeared in 1992 in the America's Cup sailing race, where it was used as the sail material in the winning U.S. boat, America3. (Cubic Tech was actually acquired by sail maker North Sails in 2007.)
Today cuben fiber is available in a range of thicknesses and weights—the lightest version weighs a mere 0.4 ounce per square meter—as well as a variety of colors. Compare that to ultralight 15-denier silnylon, which weighs in at nearly three times that. (For more, here's a good cuben fiber vs. silnylon comment thread on backpackinglight.com.)
As to the cost? Well, if only one company is making a product, and it uses both expensive ingredients and a costly production process...you do the math. In the coming years, I would expect this sort of technology to come down in price and potentially replace silnylon as the go-to ultralight fabric. But I'm not holding my breath for this to happen any time soon.
For more on outdoor fabrics and materials, check out these recent posts: