This Wye is designed to mate up exactly width-wise with the roadbed, which is 2-1/8" in SN3.  The 30-degree shoulders represent a more realistic slope found in many actual railroad roadbeds.  Any Wye in size from #6 thru #8 will fit this Wye pad.  The scale thickness is 12".  Actual thickness is 4.5mm.  Turnout is approx. 17-1/4" long, which facilitates extra length to trim to the exact switch utilized.