How to Use a Cock Ring Safely
A cock ring is worn around the base of the penis (and sometimes the testicles) to help keep an erection firmer. This is general information, not medical advice.
Pick the right type
Stretchy silicone rings are the easiest to start with. Rigid metal rings do not stretch, so sizing is important. Vibrating rings add stimulation for both partners.
Size
It should be snug, not painful. If you are unsure, go a size up.
How long
Do not wear a ring for more than about 30 minutes. Take it off if you feel pain, numbness or a color change.
Putting it on and taking it off
Use lube. Put it on before you are fully erect, and take it off as soon as you finish. If a ring is stuck and painful, get medical help.