Sprenger Check Collar, Round Links, Chrome. Available in Length(s); 25cm, 30cm, 35cm, 40cm, 45cm, 50cm, 55cm, 60cm, 65cm, 70cm, 75cm, 80cm, 85cm and Guage(s); Light 1.5mm, Medium 2mm, Medium-Heavy 2.5mm, Heavy 3mm, Extra Heavy 3.5mm, Extra Heavy 4mm, Ultra Heavy 5mm.