After an initial warm welcome for first-generation femoral artery closure devices--including a few high-profile exits--sales have stalled. Early devices are flawed, indicating the technical challenge is tougher than it looks. A dozen or so start-ups are trying to address the technology problems that have hampered the pioneers. The newcomers face high hurdles as early experience with first generation devices temper clinician and investor enthusiasm. All will have to prove, in large, rigorous clinical trials, that devices are more complication-free and are as easy-to-use as market leader Angio-Seal, and that they're at least as safe, if not safer, than manual compression. But although start-ups face a great of skepticism about particular technologies, they also inherit a $350 million market made up of devices with an average selling price of $200, which is an endorsement of this new device market. At the same time, an enormous opportunity remains in the 75% of the market that remains unpenetrated.