StopTech Sport Rotors are also available with an optional cryogenic treatment. Although cryogenic treatment is invisible to the naked eye, many fleet customers are sold on its ability to extend the service life of the brake rotor. Deep cryogenic treatment is a one-time process that permanently improves the performance and wear characteristics of metal components, from brake rotors and engine parts to machine tools and gear sets. All new StopTech Sport Rotors may be ordered with cryogenic treatment for an additional fee. Symmetric vane, split-core castings for uniform heat distribution. Black E-Coat anti-corrosive coating protects much better than competitors spray paint. Double disc ground friction surface for optimal performance and service life This extra process provides better rotor balance and creates a cleaner; more finished looking component; In addition; Rotors are inspected for balance and mill-corrected to a tolerance of less than 2oz 1982 - 1984 BMW 633CSi, 1982 - 1988 BMW 528e, 1983 - 1984 BMW 533i, 1985 - 1986 BMW 524td, 1985 - 1988 BMW 535i, 1985 - 1989 BMW 635CSi, 1987 - 1987 BMW L6, 1987 - 1988 BMW M5, 1987 - 1988 BMW M6, 1988 - 1988 BMW 535is