Schacht offers a wide spectrum of whorls to aid the handspinner in achieving the best spinning speed for the task at hand. A high speed bobbin is required for high speed and super high speed whorls when spinning in double drive. (High speed bobbins are not required for Scotch tension mode.)
What Whorl Do I Choose? It depends...on your treadling rate, the fiber you're spinning, and the type of yarn you want. There are no hard and fast rules about whorls. What is important is that you choose a whorl that helps your wheel do as much of the work for you as possible. In general: the bigger the whorl, the coarser the fiber, the thicker the yarn; the smaller the whorl, the finer the fiber, the smaller the yarn.
The Schacht Matchless and Ladybug spinning wheels both come with Medium Speed (9:1 and 11:1) and Fast Speed (13:1 and 15 1/2:1) whorls. This High Speed Whorl (17 1/2:1 and 19 1/2:1) is a great addition to your wheel. It is recommended that you use a High Speed Bobbin with the High Speed Whorl.