The normal low-cost CO2 cylinders from Lidl and Migros (with screw cap) are compatible with Philips sparkling water machines as they fit the standard screw cap systems. Migros explicitly confirms the compatibility of its cylinders with standard sparkling water devices. Make sure that these are the "old" screw cap cylinders, not the patented Quick Connect systems as with newer SodaStream models. If you are unsure, contact Philips customer service or test the fit.