The BlenderBottle ProStak features interlocking jars at the base, so you can take your protein powder on the go and mix your shake when you want it. The ProStak’s interlocking jars have individual lids, so you can carry supplements, snacks and more with or without the bottle. The covert pill tray locks into any jar lid, allowing you to carry pills and powders in the same jar. Integrated with the StayOpen flip cap, the adjustable carry loop lets you hold more when your hands are full and offers a convenient place to attach keys while at the gym. The Prostak’s screw-on lid and secure flip cap are 100 percent leak-proof. BPA and phthalate-free.