Stainless Steel Drill Jig is machined from a single piece of stainless steel. The markings on the caliber are engraved, which means they should remain legible for a long time. However, I did attempt to insert my new DeWalt drill bits into the stainless steel jig holes to test their accuracy. There are 12 sizes in my drill set: 1/16", 5/64", 3/32", 7/64", 1/8", 9/64", 5/32" , 3 /16", 7. /32", 1/4", 5/16" and 3/8". Of the 12 bits, 9 are perfect for the stainless steel drill bit caliber. The holes of the 3/32", 5/32" and 3/16" drill bits were too narrow. My drill bits were made in Germany, so I trust them to be accurate. The main purpose is to measure the size of the Measuring drills I didn't give it a single star due to the sturdy construction and etched markings.