« OK, but tricky »
They are fine, work properly, but they do not stick to the breasts when a lady is not laying on her back. In doggystyle or standing position they fall off, unless they are attached very tightly, what is quite of painful experience, so for people who do not look for a painful experience it most probably won't work. Probably a rubber seal would solve the issue.
« Well made, but not for men »
These are well-made, sturdy, with good strength. Unfortunately the diameter is too large for probably all men's nipples, and many women's. There is no way to restrict the area of suction to the nipple itself. The pleasure comes from sucking only the nipple. When the suction is applied to a much larger area, it simply causes pain. I am trying to modify the product for a smaller area of suction.