They come with rods of different lengths. You can put together different combinations to achieve roughly the length you need. Then there is also a screw adjuster on each side so that you can fine tune to the exact tension you want. I have tried one of these and the loop that fastens behind the head of the penis exerts pressure and gets painful after a while, so you do have to go easy on the tension. The one I have just has a single adjustable noose of silicone, but I have seen adverts for models with a silicone strap, and more recently one with two silicone nooses. I'd be interested to know if either of those work better than the single noose.