On Ertl's it was pretty easy. The hardest part is removing the old wheels and not damaging the axle. The Sunstar's are glued to the axle and don't roll. The Autoart's depend on the car, some snap right on and others you need to be creative. Here is Autoart's 2007 Mustang GT convertible and Ertl's 67 SS Impala, these just spapped on.