A US&S Standard Mechanical crossing bell bumped mapped which will attach to my grade crossings. This is a mesh only, not the sound. You can change the bells out by clicking on the frontbell or rearbell in cmp and click the three dots and choose the bnsf crossing bell that you want. If there is not a front or rear bell in the effects list then there are no attachment points for that crossing, thus you cannot change the bell on those crossings.