This is a nylon neckpiece only.  It has a ring to attach a lead to.  The nylon thickness is 3/16".  It has a bead to slide down to tighten the neckloop.  It will fit an 18" head.  If you need it larger, please specify in the special instructions box.  Please choose silver or gold hardware, gold (brass) is additional.  
These come in a slip, kindness, martingale or martingale kindness style. Different prices for each style.  I will need the widest part of the head measurement, usually over the ears, for a more custom fit.