Speed Stacks Competitor - Pro Series 2 White w/ Blue Flow Mat Speed Stacks Pro Series 2 (PS2) White Set with Cup Keeper G4 Timer & G4 Blue Flow Mat PS2 Holding Stem with Online Stacking Instructions The only cups endorsed by the World Sport Stacking Association (WSSA) for competition. Winner of a 2018 Family Choice Award! The "Family Choice Awards" recognize the best in children's and parenting products. Now in its 21st year, the "Family Choice Award is one of the most coveted, family friendly consumer award programs in the nation.