My cairn terrier lost his eyes to glaucoma.  I purchased this product shortly thereafter, and it has been very helpful to him and me as we make the transition to living with blindness.  My dog feels secure in this harness, and I love that it so boldly advertises his condition to other dog walkers.  I got a medium for my slightly plump aged cairn, and it fits perfectly.  It has been very durable.  I just ordered another so that I can switch them out to wash.  That shows how highly I regard this product.