Skirt steak is one of the most flavorful cuts of beef, and even though it's also one of the tougher cuts with a lot of connective tissue, it's still a great steak for grilling. Skirt steak comes from either of two separate muscles inside the chest and abdominal cavity, below the ribs, in the section of the cow known as the beef plate primal cut. The two muscles are the diaphragm muscle, called the outside skirt, and the transversus abdominis muscle, or inside skirt.
Inside and outside skirt are pretty similar; both are long, flat muscles with very thick grain that runs across the length of the muscle. These narrow pieces of meat can be about 20 to 24 inches long and three to four inches across once they've been trimmed.
Because there are only two skirt steaks per side of beef, one inside and one outside, pretty much every outside skirt from every side of beef ends up in a commercial kitchen of some kind. So when you see skirt steak at the butcher shop, it will almost always be an inside skirt.
Outside skirt is encased in a membrane which needs to be removed before preparing it. If the meat has been dry-aged, that membrane will be like paper and will peel off pretty easily. With wet-aged meat, the membrane will be wet, and it's a little bit trickier to peel it off without tearing the meat. A good butcher will have peeled and trimmed the steak before sale.

1.5 to 2 lbs. per pack