Product review (2 stars): Not For Model WED6400SB1
I should really hate this as the idler pulley roller is too large for my model WED6400SB1.  The roller is white and larger than the black roller that is only my model.  The roller actually touches the drum and locks up.

The real kicker is that the model number checker said that this would work with my model.

I have ordered another idler pulley and roller and will check back in a few days.