As for me, however, very disappointed, the quality of the role and here I mean only the change in the hardness and the plastic deformation:
I have the little black ball used relatively infrequently (about once a week to a couple of points to massage on the shoulder blade) and this is now (after 2 months) completely oval, so that a satisfactory use is hardly possible. He's like this oval that he blocked in a roll axis quasi. As an indication for use: in 74kg body weight I am leaning on the wall - so to overloading should not be there safely.
The hardness of the large and small role has also decreased sharply - and no I do not bring my subjectively lower back pain when applied but also on the plastic deformation. I can squeeze with your hand my little role, so that the notch disappears in the middle. This was at the beginning, when delivered completely different! Like in the big role. Since I have found so far only 1-2 comments in this direction on the internet, I suppose that this is an exception and I unfortunately had the misfortune to get this product. If the hardness remain constant and specifically not deform the balls I would give 5 stars!
Greetings Alex