The Waters Performance Maintenance Kit for the 2535 Quaternary Gradient Module contains all the Waters Quality Parts necessary to keep your instrument operating at peak performance on an annual basis. The Waters Performance Maintenance Kit includes the following parts: solvent filters, diffuser filters, check valve cartridges, plunger seals, o-rings, sapphire plungers, seals for plunger wash, oultet filter and vent valve rotor seal.