Non-adjustable rubber rings don't make the best beginner cock rings, as they're not very flexible and may be difficult for beginner users to remove.

Using cock rings can make the penis harder because the blood is flowing back down the penis.  if it doesn't feel good, take it off and  if you're having trouble losing your hard-on can try running your penis under cold water.

To determine which size cock ring to wear, first measure the circumference of the penis behind the balls (you can use a piece of string to make this easier). Because cock rings are normally sized according to diameter, divide the circumference by 3,14 to get the diameter measurement. Make sure the ring size is no smaller than your penis diameter.