That's bottles were needed to complete the purchase of the machine "sodastream". They have nothing dexceptionnelles regardless. They are plastic, do not go in the dishwasher and perishable ... I did not have enough to see if they used tarnish with time and limestone. CAUTION nevertheless the price, it varies from one to two I've paid 12.95 on 1 December 2013 and 20 January 2015 today are 24.75 !!!!