What is a duplex outlet? June 14, 2021 20:50 Updated Follow Duplex outlets have two sets of slots and can accommodate two plugs at the same time. Related articles Video - How to Install a GFCI Outlet, AFCI and Dual AFCI/GFCI Outlet What is a Marked “Controlled” Receptacle? What is a single outlet? What is a non-grounding outlet? Can I use a Leviton pop-up floorbox receptacle in a countertop application?