The design allows for each bogie to pitch fore and aft to take up undulations and irregularities in the rail head. The use of these sprung units affords some measure of damping out of any shocks transmitted to the coach body. This limits any tendency for the coach to wobble visibly from side to side when traversing less than perfect track and pointwork. Subjectively, the coach appears to glide along undisturbed by all but the worst track conditions. Spare springs are C60 and spare screws and nuts M2x10.
A pack contains five times the parts shown in the photo.