Environmentally friendly thick latex, resistant to fall and bite, completely does not hurt pet skin. Stainless steel hook, even if it touches the water will not rust. Button replaceable battery. When the battery is dead, you can easily replace it with a new battery (CR2032 battery) by opening the back cover with your nails. Can be hung on the collar of the pet to facilitate night travel, at any time to grasp the whereabouts. Can also be used as a key chain, is also a flash toy. 1 3/8''D x 1''H