网页2020年6月16日 · Sample vial septa. Regarding the septa, the two layers are PTFE/silicone or PTFE/rubber, but the color is not a standard for distinguishing materials, because both silicone and PTFE have different colors, this should depend on the thickness: the thinner one is PTFE layer, which should face the inside of the contact solution. June 16th, 2020.