I figured this one out on my own several years ago when I developed a latex allergy and had to use polyurethane condoms. Polyurethane condoms are less stretchy than latex so they make the condoms bigger than latex condoms which inevitably meant that if the guy I was with had an average sized penis or smaller the condom would slip off. Luckily polyisoprene condoms (the new non-latex condom) are much stretchier and don’t have this issue as often.
However, there are still times when this issue comes up. Some couples have slippage problems no matter what type of condom they seem to try. Some may just be extra paranoid about having safer sex. Others may want to cover non-phallic shaped sex toys with condoms. All of these are great reasons to use a cockring to hold on your condom.
One thing to keep in mind though is that most cheap stretchy cockrings are made of a porous material and cannot be sterilized. If you or your partner have not been tested recently or you are having sex with multiple partners it is best to use a new cockring every time.
Buy a 3-pack of Ring-O cock rings for just $6.75 at Early to Bed.