These group seals are made from food grade FDA silicone. Unlike regular seals that are made from rubber these do not have any smell or taste whatsoever, and are easy to change since they will not bake rock hard like rubber does.
When choosing group head seals , there are 2 to choose from. Thicker seals are generally used to compensate for wear and tear on the group head lugs/ group head grooves. To keep that tight fitting lock in with your portafilter as your machine ages
E61 Style Group Head Coffee Machines Group Seal with bevel and inside notch. Suits machines such as Wega, Brasilia, Expobar, Iberital, Faema, Grimac, ECM, Pavoni, VBM, Futuramat etc.