Woks, deep pans with flared sides, are the traditional vessels for stir-frying. They conduct heat evenly and efficiently, and their deep sides allow maximum surface area for cooking as small pieces of food are briskly stirred and tossed, using a long-handled wok spatula or long chopsticks. Choose a heavy stainless-steel, aluminum, or traditional milled-steel wok that conducts heat evenly and holds it well. The tight-fitting lid seals in foods to steam-cook them until done. Round-bottomed woks sit atop burners on circular metal frames. A contemporary flat-bottomed design permits the wok to be used with equal ease on electric or gas stoves.