Outside skirt (OS)
It is the diaphragm muscle and resides inside the belly of the animal, flank steaks have a very coarse grain and a great beef flavor, they benefit from a long marinade or some mechanical tenderizing, this cut is part of the forequarter of the beef.
This cut is best cooked hot and fast on a grill and is commonly used for carne asada and fajitas.
In Nicaragua it is known as arrachera, while in El Salvador, Panama, Guatemala and Costa Rica it is known as Entraña or Lomo de Entraña, although the cuts are similar, the outer skirt steaks tend to be more tender and flavorful due to their proximity to the organ meat. The outer skirt usually has a membrane that envelops the muscle and must be peeled before cooking. This cut is perfect for adding a different touch to your barbecues, but you can also use it to make shredded or shredded and grilled meat or steak.