These arms are made for the LOSI Baja Rey and are Stock length. They fit the Stock axle and have room for an extra shock if you need it.
Measurements are stock at 6″ center to center.
If you want this to fit the Metal Concepts axle you have to custom make a top Trailing arm and maybe a upper bracket to get the geometry to work out. We will be coming out with both fairly soon, so stay tuned.