Coastal Pet's Titan Chain Dog Training Collars are argon welded and chrome plated for maximum strength and durability. They will not tarnish, rust or break. Available in a X-fine 1.5 mm, Fine 2.0mm, Medium 2.5 mm, Heavy 3.0 mm and X-heavy 4.0mm. Chain dog training collars are safe, effective training tools with proper use. They are not to be used for tie out.