BSF also is known as British Standard Fine screw thread. These gages check the parallel screw thread of Whitworth form. This form has a 55 degree included angle.
WESTport provides a complete line of BSF (British Standard Fine) Thread Ring Gages. They are available in sizes from 3/16 inch to 4 inches. Free Technical support is available from our core of engineers to assist you with any questions you may have.