SNOUT CIRCUMFERENCE SHOULD BE MEASURED 1"-1.5” FROM THE TIP OF THE NOSE. IF IN DOUBT PLEASE SELECT SMALLER SIZE. Available in 6 sizes. Please use Sizing Chart for Size Reference, Snout and Neck circumference, and Loop size. For size Medium the Loop size is 7"-12", designed for snout circumference 8.25"-10.25". Nose strap layered with soft neoprene for added comfort. Made of soft strong high quality 3/4" wide nylon. Easy to use well designed durable head collar provides control to stop pulling, jumping, lunging. Allows freedom to pant and yawn.