Elma Electronic classic collet knobs are available in 4 different diameters these being 9mm, 10mm, 14.5mm and 21mm. The classic Knobs are available with and without wings for the 14.5mm and 21mm variations with all versions available with or without a white line. The knobs are fixed onto the shafts by means of Elma’s proven collet tightening method and the tightening elements are hidden from view by nut covers.