The T-bone and porterhouse are steaks of beef cut from the short loin (called the sirloin in Commonwealth countries and Ireland). Both steaks include a "T"-shaped lumbar vertebra with sections of abdominal internal oblique muscle on each side. Porterhouse steaks are cut from the rear end of the short loin and thus include more tenderloin steak, along with (on the other side of the bone) a large strip steak. T-bone steaks are cut closer to the front, and contain a smaller section of tenderloin. The smaller portion of a T-bone, when sold alone, is known as a filet mignon, especially if cut from the small forward end of the tenderloin. There is little agreement among experts on how large the tenderloin must be to differentiate a T-bone steak from porterhouse. The United States Department of Agriculture's Institutional Meat Purchase Specifications state that the tenderloin of a porterhouse must be at least wide at its widest, while that of a T-bone must be at least wide. However, steaks with a large tenderloin are often called a "T-bone" in restaurants and steakhouses despite technically being porterhouse. Owing to their large size and the fact that they contain meat from two of the most prized cuts of beef (the short loin and the tenderloin), T-bone steaks are generally considered one of the highest quality steaks, and prices at steakhouses are accordingly high. Porterhouse steaks are even more highly valued owing to their larger tenderloin. In the United States, the T-bone has the meat-cutting classification IMPS 1174; the porterhouse is IMPS 1173. In British usage, followed in the Commonwealth countries, "porterhouse" often means a British sirloin steak (i.e. US strip steak) on the bone, i.e. without the tenderloin on the other side of T-bone. However, nowadays some British on-line butchers also offer American style porterhouse steaks. In New Zealand and Australia, a Porterhouse is striploin steak off the bone.