Guerry, USDA/IMPS 185c or 185d is what you want. The USDA/IMPS 185b is often sold as being a tri-tip cut, but, it is ball tip, good in it's own right, but, not as good as tri-tip. If you can get him to order a USDA/IMPS 185 then you get both.
I'm feeling bearish, and I'm packing a Wusthof Grand Brisket slicer from MABA
Whip It Off, Chambers!
"perhaps...but then again...maybe not..."