<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Generally speaking, they are fairly lean [...] </div></BLOCKQUOTE>Correct. 'Sirloin tip' isn't really sirloin. It is actually what is known as beef knuckle and is cut from the round, at the natural seams, below where the rump is and where the top and bottom rounds are separated out. It is next to the very bottom of the sirloin but, being from the round, is leaner.