The silicone lids for pouring kefir from the Kilner Kefir Fermenter (0.50 litres) are specially designed for this jar with a wide neck. There is no clear information that these lids also fit on other Kilner fermentation jars, as these can have different sizes and diameters. Kilner often offers separate lids and weights for other fermentation jars that are designed to fit the respective jar sizes. It can therefore be assumed that the silicone lid does not fit universally on all Kilner fermentation jars, but has been specially developed for the 0.50 litre kefir set.