To facilitate the movement of  the right hand 4th finger on the foot joint keys, rollers are employed.  While rollers are always present on the C and B keys, often the player finds added facility with the addition of other rollers.

Shown are D# and C# rollers. The more common D# roller is available on most custom made to order instruments, but only a handful of production instruments (including our DiMedici 1011-JLS model).
          
The C# roller is readily available on several Miyazawa models in combination with the D# roller.
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