Shake, Shake, Shake...Shake Your Protein. With Optimum Nutrition's exclusive ON shaker cups, mixing-up even the largest and thickest protein or meal replacement shake is a snap. Each shaker cup has an Extra-Large 32 fl oz capacity and a 3 1/4" opening at the top that makes adding full-size ice cubes a simple proposition. We've also spec'd a beefy, deep-skirt cap that screws down tight to prevent leaking and a tapered bottom that fits into most automobile cup holders. And, unlike cheap knock-offs, this shaker is solid enough to survive dozens of cleanings...even in the dishwasher (top rack only). Last, but certainly not least, we're proud to say that the Optimum Nutrition shaker is made in the USA.