These 5 Litre plastic Demi-Johns are made from clear food grade polyethylene terephthalate (PET) which is an ideal material as it will not add any unwanted flavours or odours to the contents. They are supplied with a cap which is pre drilled with a grommet ready to accomodate an airlock. We recommend that you do not overfill these as the fermenting yeast will produce a froth which if overflows will cause an unsightly mess and may even assist in contaminating the brew.