Interchangeable nitrile cock rings. Latex and phthalate free. Soft cowhide leather snap. Never fear hazardous materials again! If you're sensitive to nickel, you know how the threat of a bad reaction can put a damper on even the sexiest action. That's why Spartacus developed products that are not only allergen free -- they're worry free! We recommend wearing cock rings no longer than 30 minutes at a time.