3PCS HYDRAULIC CYLINDER PISTON ROD SEAL U-CUP INSTALLATION TOOL KIT Making smaller size than gland hole by turning seal to omega shape can avoid most of damages. Includes 3 sizes to cover just about any rod seal installation job from 0.87" up. Small for rod diameters 22-40mm gland hole, 6mm cross section max Medium for rod diameters 40-70MM gland hole, 8mm cross section max Large for rod diameters 70-165MM gland hole, 10mm cross section max