The Beiter Winder PROFI HEAVY has 15mm stainless steel knobs on the spindle, instead of the 9mm ones. A small but significant change! The Beiter WINDER PROFI is used by many professional string makers, and the WINDER PROFI HEAVY has been designed to meet the highest requirements for a serving tool. Thanks to the added weight on the spindle, the centrifugal force while spinning is much higher than with the other Winder models. This allows - paired with the usual Beiter WINDER features - an extremely tight serving!