A slip-on raised face (SORF) flange is a type of flange that is attached to a pipe by slipping it over the end of the pipe and welding it in place. The flange has a raised face on the inside, which creates a seal between the flange and the pipe.
Here is an example of a SORF flange specification:
NPS: 1/2 to 24 Inch
Pressure class: 150 - 2500
Standard: ANSI/ASME B16.5, B16.48, 16.36, BS 4504, BS 1560, BS10, API 6A
Material: Carbon steel, Alloy Steel, Steel, Ductile, Duplex
Hub thickness: 0.5 inches
Bolt holes: 8 holes, 1/2 inch diameter