Xialla can be put on a flaccid or erect penis. As you begin to get stimulated and blood flows into the penis, Xialla helps the erection to build by preventing blood from flowing back out too quickly.
Many guys wonder whether the Xialla ring will inhibit blood from flowing into the penis. Xialla won't inhibit blood flowing in because blood flows in through arteries which are deep in the center of the penis. Xialla compresses the veins which are on the surface of the penis, but doesn't compress the arteries enough to prevent blood inflow.