I believe Warner brand brakes were the best ever made. The design was simple and effective. This magnet was designed for 6 volt systems but work fine with current 12 volt systems also, you will just need to crank the brake control on your tow vehicle down. This magnet has 4-7/8" ID x 8-1/4" OD and is 1-1/8" thick and the tab at the top is 2" wide. There is a wire loop on each side to secure the magnet to the hub. The is a used magnet which was salvaged from an old trailer so it does have some surface rust. It has been tested and is in good working order. Pictures may vary from the actual product but are comparable.