Rex Specs Ear Pro by Zeteo Tech was developed specifically to protect military working dogs from temporary and permanent hearing loss that can arise from noise exposure. Whether on a mission, at the range, on a motorcycle, or at an AC/DC concert — Rex Specs Ear Pro will protect your dog's ears and can limit your dog’s hearing damage over time. 
Size Guide Head Circumference: 
Size 2: 13-15 Inches / 33-38cm
Size 3: 15-17.5 Inches / 38-44.5cm
Size 4: 17.5-21 inches / 44.5-53cm