A major concern with running any carbon wheel is their durability. A rear Zipp 808 Firecrest retails for $1,624.99 alone so you definitely want these hoops to hold up. Zipp covers manufacture defects and has a great crash replacement program but the intensity of racing sometimes forces you into the wrong line or the rider in front of you may suddenly changes his sending you into a pothole. Luckily built into Zipp's Firecrest rims is an amount of flex which allows the wheel to bend under impact and hopefully avoid cracking. Check out this video of a Zipp 303 Impact Test: