High Frequency Whistle is a lightweight, compact, silent whistle. INDOOR & OUTDOOR TRAINING: The High Frequency Whistle is ideal for dog training, both indoors and out SENSITIVE DOGS: The whistle is particularly appropriate for noise-sensitive breedssuch as Border Collies GREAT FOR LONG DISTANCE: Producing a sound that travels well in open spaces ADJUSTABLE PITCH: The pitch is adjustable, so you can find the best pitch to suit your dog and it comes with a key ring attachment, to ensure the whistleis always to hand quantity of delivery:1 piece (Package contents: Only the above package contents, excluding other products.) size:5.5*0.8cm (Reminder: The size is measured manually, please allow 1-2 cm measurement error) color:silver color (Due to different monitors and lighting effects, the actual color of the item may be slightly different from the color shown on the picture.)