Trailer-Aid is the fast， safe and easy way to change a trailer tire on a tandem wheeled trailer. You pull the good tire up onto Trailer Aid to raise the flat tire up 4.5 in. for changing. It is great for horse trailers so you do not have to remove your horses in order to change the flat tire. Lifetime guarantee. Easily change flat tire on tandem wheel trailer even if you're alone. Allows you to keep cargo in trailer while changing tire. Simply drive the good tire up onto Trailer Aid. Provides 4.5 in. of lift. Made of lightweight super strong polymer.