For my nearly 15-year-old nephew (182cm, 61kg) I was looking for the matching finger dumbbells. My old with hard plastic handles and spring diameter 5mm he could not fully compress the left, the weaker hand 1x. This Schildkröt are significantly lighter and pleasantly soft. The spring diameter is only 4.5mm, and I suppose that even the steel - as opposed to my old - is softer. The weight is likely to be suitable for a young person, a petite woman or a totally untrained Bürohengst. The soft grips are also ideal for this. For everyone else, I recommend depending on the physical condition stronger designs. My fingers grip handles with hard plastic handles work perfectly, but squeak diligently and are completely odorless. The Turtle smell light and the smell is transferred immediately to the hands. Squeaking they do not yet, unlike my old.
Conclusion: Those looking for hand gentle, smooth finger dumbbells, will steer clear cornea and slight odors accepted, which is well-advised. But who wants a "proper" training effect to achieve, for example more holding power at pull-ups or climbing, I recommend stronger versions. Hard Plastic has no odor usually and thus contains fewer chemical softeners. The hard plastic is also problematic for hands that work on and off with weights.
Supplement 25.12.13: My nephew has now tried: they tend to be too easy for him. He trains with a correspondingly high number of repetitions, it is just about acceptable.
