Chrome-plated collars won't tarnish or rust. Adjust by adding or removing links to fit dog's neck. Each link adds 1" to collar size. Size is inside measurement of the collar. Allow 1 to 2" over exact neck size. Regular-Style Spiked Training Collars Chrome-plated collars won't tarnish or rust. Adjust by adding or removing links to fit dog's neck. Each link adds 1 to co