I literally wrote a book about beef, so please take this advice from me and don't focus so much on the label, but for your own education, here are the grades of beef, but remember the best way to determine this is to inspect it yourself! - Prime- The highest quality and accounts for 9% of beef that is sold. It has the most abundant marbling. The high fat content makes is more tender and super flavorful. - Choice- One step down, this accounts for nearly 75% of beef sold in the US and is the most commonly available. These cuts have moderate to modest amounts of marbling, but still offer generous beefy flavor and are perfectly juicy. This is what most grocery stores will carry. - Select- Another step down, they offer the least amount of marbling and thus will need more work to make them tender and juicy, but since a prime rib roast is already the fattest cut, they will still be easy to work with. - Unlabeled- Sometimes called "no roll" to industry professionals, you likely won't see a prime rib with this label. It is generally used for ground beef or other hot dogs. Regardless of the grade of beef, make sure your prime rib has a fat cap or "lid", a fatty top layer. This adds flavor and protects the precious meat from over cooking and drying out. I prefer getting mine from the local butcher.