Now you can measure pipe inverts and sizes fast, easily and accurately. The new and improved Pipe-Mic now has a pin setting for measuring a 1 ft vertical offset and a new round foot designed to slice through material at the bottom of the pipe. Measures the depth of pipe invert from top of rim. Measurements are more accurate because you are measuring with a plumb rod. Size pip's accurately. "New foot design insures accurate pipe size measurements. Extends out 24" and by adding the 3 ft (#PME) extension to 36" for hard to reach pipes. Made for Crain SVR and USL rods. To use:The offset is zero, so with the foot on the invert of pipe the depth can be read directly. To size a pipe: The foot is 0.33 or 4". Take the reading from the rim, pull up and take reading plus 0.33 and that is your pipe size. Example: 4" Pipe = 0.00 movement, 6" Pipe = 0.17, 8" Pipe = 0.33, 10" Pipe = 0.50, 12" Pipe = 0.67. #PME Pipe Mic three Foot Extension also available.