Our bottles are made of 18/8 medical-grade 304 stainless steel and do not have any type of liner. The bottles are double-walled stainless steel. The mouthpiece is made from polypropylene. We would not advise drinking directly from a metal top. The collar of the bottles and the screw -on cap are encased in stainless steel. There is an internal silicone washer. There is no liner inside the bottle or chemical coatings. The bottles are tested for chemicals like BPA, phthalates, heavy metals and biologically harmful chemicals.