The Trelleborg STEFA System is a completely enclosed seal providing the functions of oil seal, wear sleeve and dust protection in one unit. It has been developed to meet the ever increasing requirements of long service life, high functional reliability, environmental safety and easy installation. Trelleborg STEFA System Cassette Seals are used in heavy duty vehicle axles, hubs and industrial gearboxes.--The STEFA System is a completely enclosed seal providing the functions of oil seal, wear sleeve and dust protection in one unit. STEFA System Cassette Seals are used in heavy duty vehicle axles, hubs and industrial gearboxes.