[Sirloin Tip]
This is usually a wholesale cut, the front side of the leg from hip to knee. #167 has fat on, and #167A, called "Peeled" has the fat off. This cut is divided by the butcher in many ways. It is more tender than the other parts of the round, all of which are from the back side of the leg.
This cut consists of three sections: Tip Center, Tip Side, and Tip Bottom. The Tip Center, an oval shaped muscle, is the tenderest part of the entire Round and is often cut into Tip Steaks. The tip side is has is an oval flattened on one side and has some visible connective tissue. The Tip Bottom is irregular and smaller than the others. It contains quite a bit of connective tissue so will need longer wet cooking.
More on Cuts of Beef.