When we introduced the thinksport bottle in 2007, most reusable bottles were made of polycarbonate material, which leaches bisphenol-a (BPA). more recently, it has been shown that aluminum bottles with epoxy liners also leach this harmful chemical. So we first and foremost set out to find a safe material that adhered to our strict chemical policy. All thinksport bottles are made of 18/8 medical- grade stainless steel. We then went on to design our bottles to be highly functional and great-looking too! all thinksport bottles are super insulated to keep the contents cold or hot for hours. You can fill our bottle with ice and your favorite drink and enjoy a cold drink without the bottle sweating all over your gym bag, backpack, or desk. All of our bottles also feature a wide mouth opening (for ease of filling and cleaning) and a smaller polypropylene spout (for convenient drinking). we've also built in unique functionality like an interior mesh Filter that keeps ice from blocking the drinking spout and allows users to brew tea on the go. So, you get a high-quality insulated Sport bottle for about the same price as the other guys' basic single-walled bottles. thinksport bottles are available in multiple sizes and colors.