started out with the helix after a good bm and a lot of lube–arrived at involuntaries quickly and tried bouncing around and humping on my back–got a lot of nice rubbing for a long time but could not get to super o–fun though–tried same with the same results with the 20 mm and then the 16 mm–someday that gear will switch and i'll be off–only it will depend on what my body wants and not what i want