The three gates of hell should not be thought of as simply a version of the Seven Gates of Hell or Five Gates of hell, but made for smaller cocks. It is simply less restrictive and easier to walk around in as well as allowing greater exposure of the cocks shaft if that is desirable.
As seen in the non erect picture, the three gates of hell are fairly unobtrusive. In the erect picture you can see there is some constriction from the rings, just simply not as much as from the smaller end rings on the five or seven gates.
Largest ring: 2 inches inner diameter, Smallest ring: 1.75 inches inner diameter, Length overall 1.75 inches