The Koban Bobbin Brake Spring is to replace your inner brake spring if it gets damaged or goes out of shape. If you purchased your machine from Pinhole Quilting you will either have a Koban or post 2017 Cerliani Bobbincase. 

Note that the position of the flanges and the shape of the inner U of the spring looks different depending on whether you have a Cerliani (Italian) or Koban (Japanese) bobbincase. 

If your machine is from prior to 2017 you will probably have an original Cerliani (pre 2017) bobbincase. We recommend replacing your bobbincase with a new one if you are having issues with it. As bobbin tension is the foundation of good stitches it is important to have a reliable bobbincase.

Handi Quilter sources hooks and bobbincase from two manufacturers. You can read more about the parts for all three styles of bobbincase including the reference numbers on this PDF. 

Note that aside from the springs for the latest bobbincases we do not stock all of these parts and if you require replacements they may need to be specially ordered from Handi Quilter.