Cafelat group gaskets made from food grade FDA silicone. Unlike regular gaskets that are made from rubber Cafelat Silicone Gasket do not have any smell or taste whatsoever, and are easy to change since they will not bake rock hard like rubber does.  If you have ever struggled to change an old gasket you cannot help but notice the awful smell and the black soot that comes off the rubber.  And that is what you are potentially consuming with each drink. These have the same compression strength as rubber, but are also softer so that it is easier to create a good seal.