ISO 4928:2006 specifies performance tests of brake cups and seals for hydraulic braking systems for road vehicles; it does not include requirements relating to chemical composition, tensile strength and elongation of the rubber compound. Disc brake seals are not covered by this International Standard.

ISO 4928:2006 is applicable to moulded seals (cups or double-lipped type gland seals), 60 mm in diameter and smaller, compounded from high temperature-resistant rubber, for use in hydraulic actuating cylinders using road vehicle non-petroleum base hydraulic brake fluid conforming to the requirements of ISO 4925.