A balloon formed of a single layer of polybutylene terephthalate and polytetramethylene ether glycol terephthalate copolymer in a substantially unblended form. The copolymer has a flexural modulus of greater than about 150,000 psi. The presently preferred copolymer is Hytrelnull 8238 by DuPont. The balloon of the invention would be substantially unblended, defined as greater than about 60% by weight to about 100% by weight of the copolymer. The balloon is formed in a series of molds. The balloon of the invention exhibits high rupture pressure and low compliance coupled with good lesion cross and recross ability.