Rimba Bondage Play - Ball Stretcher in Donut Shape with Allen Key (height 4 cm) A ball stretcher should be attached around the man's scrotum, which creates a "pulling" sensation on the testicles. This ball stretcher is a 2-piece, so it is closed over the balls instead of pulling the balls through the opening. Diameter of the inside of the stretcher is 3.8 cm.  The allen key is included.