Stretch-Liquid Silicone Cock & Ergoballs.
The "Stretch-Liquid" is super elastic and easy to open, put on, and remove whenever you want. It doesn't grip as tight as the "Stretch-Hard," but that's why the inner diameters are narrower to achieve the same effect.
In the case of the Cock & Ergoballs, the inner diameter of the ring is 25 mm., and for the part for the balls, it's 35x10 mm; the thickness is 15 mm., and the length is 98 mm. with a maximum width of 45 mm.
Remember to always use a water-based lubricant with silicone toys, as silicone lubricants weaken the toy over time.
