Gold's Gym GoStak Twist n' Lock Storage Jars. 4 durable jars secure tightly to carry powders, vitamins, supplements, snacks, and more. Secure Seal for worry-free portability. Fits inside your BlenderBottle Classic or SportMixer. Mix and match sizes for a perfectly customized stack. Dishwasher safe, BPA and phthalate-free. Durable Eastman Tritan material resists stains & odors.