Are you sure you have different wheels on the front, than on the back axle?
Normally with dual rear wheels (your twin wheel set up at the back i.e. wheels on same axle) all the wheels are identical, it's
just the fronts and inner rears mount with the offset toward the center of your van and the outer rears mount with the offset
toward the outside of the Sprinter.
So, you need a set of trims (2) to fit the front axle and a set of trims (2) that face the other way for the back axle.