Track Roller Bearing Plastic Outer.75" outside diameter, .30" widthDurable celcon black plastic (a close equivalent to Delron) 2 Ball BearingChromium steel StudThreaded shaftNickel plated steelHex socket at center of stud3 millimeter hex socket, .17" deepThread M4 X .7 metric Load Capacity40 lbs Made in USARoHS Compliant Custom plastic outer, stud, guide wheel, and threaded shaft designs can be quoted upon request. Customer must test load capacity for suitability in there particular application.