Now that I have received samples of all three sizes here are the measurements:Small 13 7/8Medium 15 1/2Large 17 1/4Also noticed one of the samples had a couple links not flexing as freely as they should due to some interference at the clasp ends. Suggest inspecting your purchase closely as this could result in unnecessary discomfort to the wearer. (Apologies for the typo on the large size in the previous review)
Generally a very sturdy design with excellent finish - a heavy and quality product. Padlock is very small, which is hard to avoid with this style collar, so plan to manage some tiny keys. Note the actual sizes are bigger than shown. The large in particular was much bigger than expected measuring +1.75 over the listed size at the time of order. Small measures ~13.75Large measures ~18.25Did not order medium initially but expect it might come in at about 16.