Roller tolerance (or concentricity) is measured as Total Indicated Runout (TIR). The tighter the tolerance, the smaller the TIR dimension. According to Pete Eggen, roll specialist at Webex Inc., the company has produced coating rolls with as little as one micron TIR—that's 40 millionths of an inch variance from one end of the roll to the other. Since rolls are ground and polished with roll bearings in place, Webex uses special bearings with certified tolerances. Most coating rolls are also Webex ThermEx heat transfer rolls often specified with a chrome-plated finish. To ensure such exacting tolerances on coating rolls, the company uses an electronic gauge to measure roll TIR. Mr. Eggen stated the company routinely produces tight tolerance coating rolls with diameters of six to 24 inches and larger for lines running as fast as 3000 fpm.