Did not work for me at all..
The problem with so many of these tunnel toys, is that fundamentally they are bad designs. There are four parts of the design that seem to be wrong : (1) The top part of the toy must be large enough to require a decent effort to insert and with a gradual taper to ease open the hole (i.e. not a hemisphere at the top) (2) The neck, between the base and the inserted length must be greater than the thickness of you actual hole - such that the top pops in, and then the hole can clench around the neck (3) the bases are rarely created large enough and often are the same size (or less!!) than the inserted part - these bases need to be larger, whether round or oval, to ensure the base cannot ease into your hole. (4) material - the metal ones i have tried ( these mostly had problems (1) to (3)), were not functional for me at all. I tried an Oxball (expensive) , and that had totally insufficient rigidity - it just folded up! My perfect tunnel plug would be rubber / silicone, about 7.5" long, 4" inserted (max. diameter 3.5"), a 2" neck, with a base 5.5" diameter. The tunnel would be around 1 1/4 - 1 1/2". That would pop-in, stay-in and provide a reasonable opening.
