All Dr. Slick Glass Bobbins have Delrin feet for smooth tension on the thread spool, and these ones have dual glass inserts for smooth application of thread to fly. These funnel shaped glass inserts allow for a smoother application of thread or other materials as the bobbin is rotated, and they cause less breakage than traditional pipe or straight edged inserts.

• Dual glass inserts
• Delrin feet
• Several sizes available