The article traces the origin of several generalized conformability bounds for split and splitless piston rings used in the automotive industry to troubleshoot and better design piston engines and compressors for lesser emissions and oil consumption by presenting an irregular power cylinder bore shape through individual Fourier waveforms of a different order. The work also elucidates the origin and capabilities of the prematurely forgotten specialized ring-bore contact models of the 1940s for single-order bore deformation (round and oval), according to which a ring-bore seal breach occurs only near the ring ends and emerges with any bore deformation. With the aid of this information, the report explains that the split ring generalized models’ theoretically defined conformability bounds are largely conventional categories that become sufficiently compelling engineering tools only by adapting the models to the experimentally observed or analytically asserted ring-bore clearances near the ring ends and considering the ring and bore design and production deviations from the theoretical models. The study further demonstrates that different researchers’ semiempirical versions of these bounds were spinoffs from the author’s analytical model of 1990. The article’s information helps engineers design piston rings and the associated components with better functional and tribological properties.