The Nastran file type supports both Nastran and Nastran-L database surface import. The regular format (Nastran) reads 8 characters for real values whereas the large format (Nastran-L) reads 16 characters. Both formats are based on the commercial software product of the same name (Ref. 17). Only CQUAD4, CQUADR, CTRIA3 and CTRIAR elements are supported and are imported as shell surfaces. Also note that only triangles are supported for import; as a result, quads will be converted to triangles during import by splitting the quad elements in half.