The Acrylic Cock and Ball Crusher is a very effective device designed for CBT.
Two acrylic plates are connected at the top with a hinge and separated by two 7cm screws at the bottom of the device. The back plate has a hole for putting the cock and balls through. Wing-nuts are used on the screws to bring the plates closer together. You can tighten the crusher all the way, making the open space only 1.5cm” wide. Or you can make the space almost 6cm wide for a lighter crushing.
The front plate is clear acrylic, and the back plate with the cock and ball-hole is dark-tint acrylic. Both acrylic plates are 13cm across and 18cm long.