Microlon Compound-90 (C-90) is a specially formulated metal treatment for manual transmissions and differentials. It reduces performance-robbing and wear-causing friction on gears and other metal surfaces. C-90 treats the metal surfaces with a durable micro-thin dry super lubricant film for reduced friction and noticeably smoother operation and protects against corrosion and scale. You only need to treat your manual transmission or differential once to reduce maintenance and extend their life.