Color-Coded University of North Carolina Screening Probe 1-2-3-4-5-6-7-8-9-10-11-12 mm markings. Probes are used to measure periodontal pocket depth in millimeter increments. The millimeter measurements are precisely cut into the Probe tips. Color-coding is applied to probes under extreme temperatures so that the color penetrates the surface of the tip. Probe tips undergo additional tight-tolerance grinding to achieve the desired readability for each marking.