JW Bicycle Products 5 Bolt Junior chainrings are made from 2.5mm thick 6061-t6-billet aluminum to keep the weight down for the little guys. Completely CNC machined with one thing in mind - PRECISION! This will be the truest running gear you have ever used. Patterns are designed for stiffness to transfer the power where it needs to go while at the same time keeping weight to a minimum.