This butt plug by Hung System toys is a big boy, but designed to be used with a full strap on system. Use the Yoo Hoo plug on its own, it's bigger enough to sit on and as its smooth and ridged. Slide down its 6.5cm diameter shaft straight to the base. As the Yoo Hoo Butt Plug has a hole under its base it fits perfectly with the Hung System add on. Soft rubber PVC that's firm yet supple.