This pack is an add-on pack for T3D-033-000 650cu ft Mail Trailer. This pack contains two alternative style tops to replace the full door version in the original pack. Both tops are half-door style - one with the doors open and one with the doors closed. Simply print off T3D-033-000 except for the trailer top and drop one of these in its place. This allows you to create a variety of mail trailers at a sorting office or as often seen at a railway station.