Material: 304 stainless steel/SUS304 Leash attachment: O-ring attachment, easy on and put off Safe and effective way to train your dogs with our chain collar, designed to tighten under tension, correct the wrong behavior by pulling the leash with a gentle but effective feedback Size Guide: For choke collars, measure the circumference of pet's neck and add 2"–3" 2.5 mm thickness, 0.8" loop width, adjustable from 14" to 17" 3 mm thikcness,1.2" loop width, adjustable from 18" to 21" 4 mm thickness,1.6" loop width, adjustable from 20" to 25" Safe effective dog training tools with proper use, these training collar provide a heavy-duty safe alternative to standard choke chains For dog relate product please search brand ‘SGODA'