Holds most stemware, up to 3 1/8" diameter base, including wine, martini, and margarita glasses. The wine glass holder fits into most standard 3 1/2" diameter cup holders. Just place the wineglass holder into a cup holder and slide the base of your stemware into the slot in the top. Then simply slide your glass out to take a drink and replace it into the wine glass holder between sips. The Wine Glass Holder allows for easy placement and no worry of tipping or breakage.