8milelake Hydraulic Cylinder Piston Rod Seal U-cup Installation Tool kit Includes 4 sizes to cover just about any rod seal installation job from 3/4" up Small for rod diameters 3/4" & up with a seal cross section of 3/16" max. Medium for rod diameters 1-1/4" & up with a seal cross section of 1/4" max. Large for rod diameters 2" & up with a seal cross section of 3/8" max. X-Large for rod diameters 2-3/4" & up with a seal cross section of 11/16" max.