Standard Seals - Class 1 Service Kits are standard,and contain polyurethane and Buna-N seals for standard hydraulic service. These seals are suitable for use when hydraulic (mineral-type) oil is the operating medium. The recommended operating temperature range for Class 1 seals is -10°F (-23°C) to +165°F (+74°C). The seals contained in these kits are supplied as standard on all Series 2H, VH, 3L and 7" and 8" bore 3H cylinders manufactured after Sept. 30, 1990 for Class 1 hydraulic (mineral) oil service. The seals contained in these kits are interchangeable for hydraulic (mineral) oil service on all Series H, 2H, VH, L,2L and 3L cylinders manufactured prior to Sept. 30, 1990.