The WooLee Winder is particularly nice for even plying, as you don't need to stop to move the yarn guide as you do on manual flyers. The tradeoff is a very slightly heavier, less responsive feel due to the inertia and friction of the level-wind mechanism. It is very important that you keep the mechanism clean and properly lubricated for best results. Not a big deal, just beware that it's important.
The flyer speed ranges from zero to about 1400 RPM; a bit slower than the other flyers due to friction and wind resistance.
The tachometer sensor magnets are used to determine the RPM of the flyer; the Pro and Classic V2 minispinners are able to display this information when we begin producing our LCD display, which plugs into the foot switch jack.
If you wish to show RPM when the display is available, for an additional $15.00, you can order these magnets.