Pet Blinkers give you the added security and peace of mind knowing you and your pet are visible at night. Whether going for a jog or just want extra attention to your pet. Just attach the Pet Blinker to your pets collar and be seen up to 1/2 mile away. Requires 3 AG3 lithium cell batteries (included). Small - 2 1/2" H - Light flashes in red white and blue colors. Large - 3 1/2" H - Light flashes in pink and jade colors.