Coastal Pet Products DCP552520 Titan Medium Chain Dog Training Choke/Collar with 2.5mm Link, 20-Inch, Chrome Titan dog training choke/collar is excellent for gentle control This medium quality chain is argon welded and chrome plated for maximum strength and durability It will not tarnish, rust, or break and recommended for professional training Use only when dog is attended on leash and is sized by total length, including the rings Measures 20-inch overall length and 2.5-mm link diameter