Herta Henry is a fun singlestroke and herta étude that is a lot more challenging than it looks. You will have to mind what I call the “herta paradox”: hertas consist simply of legatos on one hand and doubles on the other hand, but putting them together in the herta rhythm mysteriously creates a tendency to unnecessarily tense up on both figures in order to achieve correct timing. The skeleton variation will give you a benchmark of how the as-written exercise should feel if you are truly relaxed.