Dental Explorer Probe UNC 15/23: 15 UNC Color-Coded Probe End Color Coded Williams Marking 1-2-3-4-5-6-7-8-9-10-11-12-13-14-15 probes are color-coded with accurate, smoothly finished black markings, which will not chip, flake or fade. 23 Shepherds Hook Explorer End is used for caries and calculus detection, exploration of pocket characteristics, furcations and restorations.It is a perfect instrument for locating and opening of small canal orifices for an Endodontic procedure.