10mm Screwo Top PP Caps. We provide the protection of PTFE and the resealing ability of silicone with our septa and seals to fit our autosampler crimp top vials. This seal includes a two sided PTFE septa with silicone in the center. Rated 4.8 /5 based on 223 customer reviews. 8mm pp caps pp cap pp cap for hplc pp cap with center hole screw pp cap.