The hard-shell or crispy taco is a tradition that developed in the United States. The most common type of taco in the US is the hard-shell, U-shaped version, first described in a cookbook in 1949. This type of taco is typically served as a crisp-fried corn tortilla filled with seasoned ground beef, cheese, lettuce, and sometimes tomato, onion, salsa, sour cream, and avocado or guacamole. Such tacos are sold by restaurants and by fast food chains, while kits are readily available in most supermarkets. Hard shell tacos are sometimes known as "tacos dorados" ("golden tacos") in Spanish, a name that they share with taquitos.