The Starrett 644 Dial Depth Gage is for longer ranges, and is accurate and simple to use. Put the contact on the work to be measured and push the gage head down until the base stops at the reference point and take your reading. Furnished with three rounded-end contact points to cover the range. Flat end contact points are also available on special order. The zero setting can be checked with the (shortest) contact in place by pushing down on a flat surface. 0-3" Range, .001" Grad, 0-100 Dial with Case.