TyreBeads Tire Balancing Beads - 4 bags of 4 oz (16 total) fits 4 tires Includes 4 bags of 4 oz each (16 oz total) + FREE Applicator Kit, FREE Filtered Valve 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 "Tire Balancing Beads - Installation / Applicator Kit", just enter "B00HTUDHYU" in amazon search box above if you need instructions on how to use it. Additionally, you can add our Filtered Valve Cores, just search for "B00LTCL0H0" on Amazon. 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.