Center grooved, universal design: 1-1/8" steel ball bearing roller and axle kit. Roller has a steel inner race and 1/4" hole. Installation kit includes assorted axles used to repair sliding door roller assemblies. Roller Diameter: 1-1/8", Roller Width: 5/16", Inside Diameter: 1/4", Roller Edge Type: Concave, Roller Material: Steel - Ball Bearing. Please click on the pictures above for detailed measurements.