Lyman's Custom Fit Loading Blocks are designed to provide a precise fit for a family of cartridge sizes. Made from tough, durable polymer, Custom Fit Loading Blocks hold 50 cartridges and will securely nest together for easy storage. Custom Fit Loading Blocks come in 6 sizes to match up with a large variety of cartridges. Each block is clearly marked with the diameter of the cartridge storage hole WARNING: This product contains a chemical known to the State of California to cause cancer, birth defects, or other reproductive harm.