Herm Sprenger Prong Link This link extension for Herm Sprenger Prong Collars allows custom fitting of collars to suit individual needs. Each link is made of high-quality German steel and is available in four weights. Features: One link per order Each link adds 1 1/8 L to collar Adds length to create a custom fit Item Specifications: Sizes: Lightweight: 14 (2.25mm) Mediumweight: 18 (3.0mm) Heavyweight: 20 (3.25mm)