The fan has eight aluminum blades that hold all standard Architect, Engineer, and Metric calibrations as well as a 6 in.
Imperial ruler.Architect - 1/32, 1/16, 3/32, 1/8, 3/16, 1/4, 3/8, 1/2, 3/4, 1, 1 1/2, 3Engineer - 10, 20, 30, 40, 50, 60Metric - 1:20, 1:25, 1:50, 1:75, 1:100, 1:125 Aluminum Drafting Fan 8 blade tool.