The high and aggressive apex of the widest part of the toy with a long taper to play with is what makes grunt play possible. All the sizes are now under 6” tall, keeping all the action off the second ring.  The tips on the larger sizes are less abrupt than before and the necks on many of them are larger: better for gaping and stretch practice.  The largest sizes (LG, XL, 2XL) also now have a notch incorporated into the plug.  Borrowing on this concept from other large girth toys it does two things: allows for a bit more give and flex when training up, but also reduces pressure on the coccyx, or, the prostate depending on orientation.