These are made in Montana by Rite Bobbin Co. These are the original tension adjustable bobbin with the famous 1/4 turn click stop. To add thread spin off click stop, pull cover and insert thread spool . The plastic discs are spacers used to adjust the spool tension. You turn the click stop to adjust the tension of your the thread.
The Standard has a ceramic tip and works well with standard thread, coarse saltwater threads and Gel Spun.
The Half Hitch Bobbin has a polished tip to allow you to make half hitches and create a whip finish by wrapping thread around the tip.
The Mag Bobbin is designed for making saltwater flies and bass bugs. The Mag is ideal for glue spun thread and making big bugs with thick thread. This was a long time favorite of Bass Bug tyer Chris Helms of Ohio.