19990-A Feeler Gage Set is a 20-piece set that includes both inch and metric markings. This makes it easy to take measurements in either system. It has high carbon spring steel blades that are made for durability and accuracy. Each blade has an inch or metric marking, depending on the type of application you need it for. The length ranges from 12 in., while the thickness ranges from 0.001 in to 0.03 in.. The material used for these blades is high carbon spring steel, so they will not bend or break easily even when used on hard surfaces like metal or concrete. Feeler Gage Set will help you determine the perfect fit with its accurate measurements and durable construction.