ISO 5597:2018 establishes the preferred range of nominal dimensions and associated tolerances for a series of hydraulic cylinder rod and piston seal housings for reciprocating applications in the following range of dimensions:
- for cylinders of 16 mm to 500 mm;
- for rods of 6 mm to 450 mm.
An additional range of seal housings is detailed in this document to meet the reduced envelope requirements of the 160 bar (16 MPa)[1] compact series of ISO 6020‑2; these smaller section seals require stricter piston rod and cylinder bore tolerances. The range of dimensions is as follows:
- cylinders of 25 mm to 200 mm;
- rods of 12 mm to 140 mm.
ISO 5597:2018 does not give details of seal design, since the manner of construction of seals varies with each manufacturer. The design and material of the seal and any incorporated anti-extrusion components are determined by conditions such as temperature and pressure.
ISO 5597:2018 only applies to the dimensional criteria of products manufactured in conformity with this document; it does not apply to their functional characteristics.

[1] 1 bar = 100 kPa = 105 Pa = 0,1 MPa; 1 Pa = 1 N/m2.