The top sirloin butt is the boneless top of the sirloin, and USDA prints it two ways that matter: whole boneless (IMPS 184) and center-cut (IMPS 184B). The boneless 184 holds the gluteus medius, the main top sirloin muscle, plus two small gluteus muscles and the cap. The bottom sirloin and the butt tender are already off. The center-cut 184B is the gluteus medius alone: every other muscle comes off, and the surface fat is trimmed to flakes no deeper than an eighth of an inch. The cap itself, sold as coulotte or picanha, has its own article. This one is about the specs between whole and center-cut and what the difference costs.
The 184 family
| IMPS | Name | What it is | IMPS weight classes |
|---|---|---|---|
| 184 | Top sirloin butt, boneless | The gluteus medius, two small gluteus muscles and the cap | 8 lb to over 14 lb |
| 184A | Semi center-cut | 184 with the cap off | 7 lb to over 13 lb |
| 184B | Center-cut, cap off | The gluteus medius only, surface fat trimmed | 5 lb to over 11 lb |
| 184C | Untrimmed | 184 with the sacrosciatic ligament allowed to stay | 8 lb to over 14 lb |
| 184D | Cap | The cap muscle alone (coulotte, picanha) | 1 lb to over 4 lb |
| 184E | 2-piece | 184 with the cap seamed off and packed with it | 8 lb to over 13 lb |
| 184F | Center-cut, dorsal side | The top portion of the gluteus medius, the "baseball cut" | 3 lb and under, or over |
Watch the words "cap off". The semi center-cut (184A) and the center-cut (184B) both have the cap off, but only 184B takes off everything else and trims the fat. A quote for "cap-off top butt" needs the number.
What USDA prints
The daily boxed beef report carries three top butt lines that trade: the Choice boneless 184, which prints almost every day; the Choice center-cut 184B, which USDA has printed since 2017 and which printed on 202 of 253 sessions in the last year; and the Select boneless 184. A heavy split of the boneless prints now and then, on 40 days so far in 2026. The light split and the 2-piece have not printed since 2001 and 2006.
Over the last 12 months the median Choice boneless traded at $5.48 a pound, the Choice center-cut at $7.12, and the Select boneless at $5.16. The center-cut carried about a quarter of the Choice top butt pounds.
What the center cut costs
The center-cut traded over the boneless on every day both printed since 2017. Over the last 12 months the median premium was about $1.76 a pound, or 33 percent, and four days in five it sat between about $1.20 and $2.42. A pound of center-cut is all gluteus medius with the fat trimmed; a pound of boneless still carries the cap, the smaller muscles and more fat. The premium is the price of that work and that loss.
The grade gap is small next to it. Choice boneless traded over Select boneless on 80 percent of days in the last year, by a median of 21 cents a pound.
How the two lines move
Over four-week stretches the center-cut followed the boneless fairly closely, and the boneless followed the Choice cutout a little more than it followed the strip loin. Day to day the center-cut is far noisier: it moved more than 5 percent in a day on 35 percent of days in the last year, against 6 percent for the boneless.
For a buyer the choice is labor against price. Buying 184 and cutting in house keeps the cap and the trim on your side of the table; buying 184B pays the packer to do it.