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.