These headspace gauge sets will allow you to determine the headspace on your .22 LR firearm. Seven gauges are included to indicate headspace from .039″ to .045″. Each gauge is marked with its size. Use these to check existing firearms, when installing prefit barrels, or along with Shim Kits to fine-tune headspace to match your ammunition. Headspace gauges are made from stainless steel. The 3-D printed storage box is included.