THE CONVENIENCE OF A HITCH STEP AND THE SAFETY OF A SONAR BACK-UP SYSTEM. Trucks and SUV's are great for haulin large loads and people. But sometimes it can be a challenge to back out of your parking space. The Dolphin SONAR STEP gives you easier access to your truck bed or roof rack. Plus, it has a sonar alert system that detects objects behind your truck or SUV. The SONAR STEP plugs into your existing 1 1/4" or 2" trailer hitch. It sends signals to a wireless receiver that fits into any 12 volt socket. The reciver emits three different beeps that lets you know how close you are to object behind your vehicle. Installs in 30 seconds and comes with a locking hitch pin. For use with hitches over 15" from road surface.