We use polyurethane seals without any reinforcements or inserts. That what we came to after talking to mechanical engineers who do the materials for the space program. No need for exotic materials other than for marketing purposes. Teflon is good when there is a chance for a dry friction. It is not the case for the soft top hydraulics. And teflon is not flexible, more difficult to install and higher chance to crack because it is a thin layer. Teflon does not bound well to the polyurethane and there is a risk of separation when using teflon reinforcement. It is usually used as a coating for something than might anticipate a catastrophic lubrication failure and high friction. A/C compressor pistons for example. No need to take a risk and increase costs for soft top hydraulic cylinder - slow and well lubricated. There is also viton or rather similar materials under different trademarks. Those are soft and easy to install, but more difficult to manufacture custom seals and they are not really aimed at the hydraulics. They are great in environment with no pressure to hold and a lot of friction, like cylinder valve stem seals. Not really for us. There are other exotics that people use when really needed. Those withstand huge temp. variations and radiation. If anyone is launching R129 or A124 into space, let me know. So, high quality, durable polyurethane. Happy topless cruising!