Recent advances in metastability theory allow designers to more accurately model the response of clocked latching devices to asynchronous inputs. Understanding of these developments can impact the latency of synchronizers by giving the designer an accurate determination of the Mean Time Between Failures of a given design. This talk explains the new developments and how to implement this knowledge. A theoretical worst case bound for metastability is shown and a practical worst case bound is discussed. These discoveries were driven by a need to understand the failure rate of flops in a negative feedback situation but the knowledge gained has a universal impact.