This part of ISO 7425 specifies the dimensions and associated tolerances for a series of piston seal housings to accommodate elastomer-energized, plastic-faced seals used in reciprocating applications. It is not the intention of this part of ISO 7425 to stipulate details of seal design, since the manner of construction of seals varies with each manufacturer. The design and material of the seals and any associated anti-extrusion components are determined by conditions such as temperature and pressure. This part of ISO 7425 applies only to the dimensional characteristics of products manufactured in accordance with this part of ISO 7425. It does not apply to their functional characteristics.