The Expression Pedal of Classic Hammonds had a very unique response or “curve”. No other Expression/Volume pedal has ever matched it’s unique feel. Many Hammond Players have developed their styles with regard to this. The Exp-50J is the same size, has the same “feel”, and most importantly, has that same “curve” as the Classic B-3. Every Hammond player will feel right at home wiith this pedal. The SkPRO/SkxPRO/XK-1c, and Legacy Sk/Skx series are all “default” set to accept this pedal.