The Parks-McClellan (Remez) algorithm is a filter design algorithm that is optimal in the sense that it minimizes the maximum error between the desired and realized transfer functions. Many implementations of this algorithm exist, including in GNU Radio and SciPy. However, some of these have issues such as numerical stability for some filter design problems. I will give a summary of the Remez algorithm, why there are different possible implementations, and why some may be better than others. I will also explain how to use this algorithm for some practical filter design problems. The talk is intended partly as publicity for the pm-remez Python/Rust modern implementation by the speaker and partly as a tutorial on filter design.