The document discusses the RPI removable partial denture system developed by Krol. It describes the key components of RPI clasps - the rest, proximal plate, and I-bar - and how they have been modified from Kratochvil's original design. Specifically, the rest is less extensive, the proximal plate contacts less of the guiding plane, and the I-bar is located in the gingival third. The document also outlines three approaches to applying the RPI system based on the design of the proximal plate and its contact with the guiding plane. Finally, it notes that the RPI system has been further modified by Kroll into the RPA system through the addition of an Akers clasp.