You Bottles in 500ml version is made of stainless steel (18/0 out, 18/8 inside), which is the most suitable material for food use. The steel used is resistant and ensures prolonged use over time, without to change flavors, offers a thermal maintance of 12h fot HOT drinks and 24h for COLD ones. Free of bisphenol (BPA FREE), all bottles are certified to guarantee the suitability of a product for food use.