The title of ASME B16.5 is Pipe Flanges and Flanged Fittings
NPS 1/2 Through NPS 24 Metric/Inch Standard. This standard is about 230 pages.
Let us know if you have a specific question about the 4-inch nominal pipe size Class 150 flange. You may need to clarify your request too. By threaded I am guessing that you speak of a reducing flange using a 4-inch flange that is threaded for a smaller size. Is this correct?
BTW, consider discussing flange classes such as Class 150 instead of 150 pound. Many people use 150# or 150 lb, left over from another era. The ASME B16.5 flange nomeclature changed from 150 lb to Class 150 with the 1973 revision.
Regards,
John