The Meiki no Himitsu Secret Onahole features an immaculately designed inner hole, curving just right and filled with bumps and ribs. Stretchy and textured, the hefty masturbator incorporates a butt for extra levels of realism. The toy is awesome to use on its own, of course, but makers G-Project particularly recommend it for inserting into air dolls.
The Meiki no Himitsu Secret Onahole features: