The Performance Tool W80541 20-Piece Blade SAE and Metric 12" Extra Long Feeler Blade Set is a must-have for any mechanic or DIY enthusiast. The set provides precise measurement of gap clearance widths between two parts, and each blade is permanently marked with the blade thickness for easy identification. With a flexible design, the blades can be stacked together to gain increased values, providing greater flexibility for various tasks. The high-quality steel construction ensures that the blades are durable and long-lasting, while the set includes 20 blades of varying sizes, with both decimal size and metric equivalent etched on each blade. Ranging from .002 to .040 inches, this set is perfect for a wide range of applications.