TyreBeads Tire Balancing Beads - 4 bags of 10 oz (40 total) fits 4 tires + FREE Applicator Kit Includes 4 bags of 10 oz each (40 oz total) + FREE Installation Kit, FREE Filtered Cores, FREE Red caps These are premium internal tire ceramic balancing beads. Reusable, super hard, durable, and eco-friendly - will not rust, clump, or melt Pour them in during mounting or apply through the stem. Good rule of thumb is 1 oz per 10-12 lbs of tire To install these through the valve stem you can use the included THESE ARE NOT GLASS, which is a softer material that has a tendency to break down into powder, which is susceptible to clumping and is a health hazard.