BSW also is known as British Standard Whitworth. This gage checks the internal threads of British Standard Course Screw thread pieces. This is an older standard and this kind of thread form is mostly used for replacement parts. These are available in sizes from 1/8 inch to 6 inches.
WESTport provides a complete line of BSW (British Standard Whitworth) Thread Plug Gages. They are available in sizes from 1/8 inch to 6 inches. Free Technical support is available from our core of engineers to assist you with any questions you may have.