The original Magefesa spare part should be replaced in the following way:

Suitable for STAR 12 – 14 Qt. / ALUSTAR 16 – 23 Qt. Diameter: 10.5″. Remove the worn gasket and clean the channel of the lid housing carefully. Moisten the new gasket into the channel of the lid housing. Helping yourself with a spoon, press the sealing gasket all around against the lid until it gets completely fitted into the channel of the lid housing. When storing, place the lid facing downwards allowing for ventilation.