The Boston Shaker for the skilled pro. The combination of two weighted cups is a classic choice for the seasoned bartender. They’re made to last behind the busiest bar, in the harshest commercial dishwasher, and through a thousand drops on the floor. Cups are 28 oz / 825ml and 18 oz / 525ml. Seals tightly & Opens easily (but only when you want it to!) Made from Stainless Steel 304 (That's the high-quality, food-grade kind). Weld: Circle-welded, so the bottoms will never fall off!