This Wye is designed to mate up exactly width-wise with the roadbed,.  Any Wye in size from #6 thru #8 will fit this Wye pad.  Wye is approx. 19-7/8" long, which facilitates extra length to trim to the exact switch utilized.  Your choice of 30- or 45-degree slopes are available, along with Mainline height of 5mm or Branchline/Siding height of 3.5mm.