An erection ring, also known as a cock ring, is a device worn around the base of the penis (or sometimes around both the penis and testicles) to help maintain an erection. They assist with erectile dysfunction (ED) by restricting blood flow out of the penis, making erectionions firmer and last longer. They can also be used to increase sensitivilty. Silicone or rubber varieties provide a comfortable fit due to their stretch nature whilst metal rings provide a more ridgid, tigher fit. Some rings may have a mechanism to allow the to be adjusted or have a small vibrating motor to add stimulation for both partners.