Excel's boneless outside beef skirts with diaphragm meat cook beautifully at high heat, ideal for preparing quality beef dishes with short cooking times. The skirts are one of the most flavorful cuts of beef with little preparation required, perfect for signature menu items. Excel's Outside Skirt is the diaphragm muscle which is located at an angle between the 12th and 6th ribs on the medial side of the navel. It is produced from the primal navel.