In cigars, "robusto" is a vitola that is short and broad, packing a big smoke in a not-too-big package. A similar idea appears to be at play here: briars that are medium in length, but big on bowl and chamber.

Note: While all of our other pipes are photographed individually, these are not, and you may expect some reasonable cosmetic variation between the example we've photographed and the pipe you've received.