One pet collar safety light in blue. Batteries are replaceable. Includes 2 extra batteries to extend the life of the collar light. Average battery lifespan is 30 hours. To use, press on or squeeze the middle of the light. You can click through the 3 light settings, steady glow, fast blink, and slow blink. The 4th click will turn it back off. To change batteries simply pop off the back of the case of the collar light. There are no tools necessary.