lululemon cool racerback (black, 8) lululemon this versatile tank has a slim racerback that stays put—and out of your way—when you're on the move. measurements: 30" long size 2 width: 11" across under the arms size 4 width: 12" across under the arms size 6 width: 13" across under the arms size 8 width: 14" across under the arms size 10 width: 15" across under the arms size 12 width: 16" across under the arms