In a mixed mode file, the background material for an entire NSC group may be defined by the Glass column for the NSC surface in the LDE:



Note, however, that because the entry and exit ports serves as an interface between the sequential surfaces and the NSC group, these ports can have refractive power if a non-air glass is applied to the Non-Sequential Component surface in the LDE. 

If this is not a desired solution, yet a “background” material is still desired, then the same solution which is described for a pure NSC system can be utilized in the NSCE of a mixed mode design.