From West Seattle Runner (WSB sponsor):

We’re giving out Brooks Bucks!! Try on a bra (we’re doing fittings) or shoe gets and pop a Brooks Bucks Balloon which will reveal the amount of Brooks Bucks you win ($5-$25!) Brooks Bucks are to be used the night of the event on any Brooks product (bra, apparel, shoes). Since we are popping balloons, we will also pop the cork on some bubbly!!