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.