Martingale collars (also called limited - slip collars) are usually made of
flat nylon with a smaller fixed - length section (made of either
nylon or a short length of chain) that, when pulled on by the
leash, shortens up tightening the collar around the dog's neck, to a limited extent.
Please come to class with a
flat collar or body harness, a 6 - foot leather or
nylon leash, small soft treats and up - to - date vaccination paperwork.