The unique three-piece design, made from High Density Polypropylene plastic, includes (1) a large 20-ounce liquid capacity cup, (2) a tight, snug, leak-proof, triple-threaded screw-on flip-top cap with an easy-flow spout for convenient drinking, and (3) a thermoplastic rubber inner seal (not an inferior foam core seal like most companies use, which eventually breaks down and leaks!) for reliable leak protection. This seal is attached to an internal fine-mesh mixing sieve that locks securely to the cap and ensures a perfectly blended drink every time. This will be the last shaker cup you'll ever need to purchase.