Laser Markings: mm1-2-3-4-5-6-7-8-9-10-11-12-13-14-15 Color Coding: between 4-5mm 9-10mm 14-15mm Periodontal probes are used to locate, measure and mark pockets, as well as determine their course on individual tooth surface. The typical probe is a tapered, rod-like instrument calibrited in millimeters, with a blunt rounded tip.