Spherical shapes trigger their own stimulus when penetrating the body. The up and down movement stimulates the prostate or G-spot . If several beads are inserted in succession, the muscles are alternately stretched and relaxed. These spherical toys are also very suited to train the muscles. With a little practice this effect can be increases by attaching weights on models with loops. Attention: If these toys are not secured during anl play, the beads can travel up the body against the peristalsis and may only be removed at the hospital. It is therefore imperative to insure the toys don't "get lost". Best to secure them with an additional string.