The tenderloin is a lean muscle that runs along the inside of the spine atop the ribs. Because it is one of a few muscles that gets very little use out on the pasture, it is very tender.
The tenderloin is lean so keep a close eye on it as you cook it...you can always put it back on the grill or in the pan but once it's overdone, there's no going back.
Each Red House Ranch beef tenderloin package weighs about 3.5 pounds.