An extra bearing option for Amacoil/Uhing rolling ring linear drives doubles the axial thrust capacity without forcing users to redesign for a larger size drive. Model RG linear drives are available with 3- or 4-ring bearing assemblies inside the drive unit. Adding the fourth ring essentially doubles the axial thrust output, yet only slightly increases the length of the drive housing. For example, a 3-ring 30 mm drive (model RG3-30) supplies 60 pounds of axial thrust and has a 150 mm (6 inch) long housing. The 4-ring version (model RG4-30) delivers 120 pounds of thrust, yet the housing is only 30 mm (0.5 inch) longer than the 3-ring version. For the company's drives sizes 40 mm and larger, the 3- and 4-ring drive units have identical dimensions.