Please measure dog mouth distance and bust to choose the suitable size before buying. Because dogs of different body type need to use different size of this product. Every dog harness guiding device can adjust, please check this item picture. When pet to adapt to this anticollision device. At that time, you see them re-establish their confidence. They learn to trust this device because this device guide them to avoid hit hard object and protect themselves. When it come a hard stuff, as bumper to protect their , face and nose from contact, and can remind the BLIND DOG of obstruction in front. Suitable for pet with visual impairment, such as elderly pet and pet with eye diseases. Blind pet collar doesnot affect daily activity, such as sleepingandeating. Colour: As Shown Material:Polyester + rubber size:M Package Contents: 1 * Harness for Blind Dog Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.