Not exactly a "cab" but close enough. The rings and marble size are very picky. It can easily become too tight, but the slightest looseness that lets any ring change position will cause the marble to fall out.
Rings used: 18ga 3/16", 18ga 1/4", & 16ga 5/16".
The four 16ga 5/16" rings around toward the back, holding everything together. They can be seen in the side-view picture.