One solution are double-delta seals that use of PTFE components riding energized by an O-ring. The O-ring creates a balance between the desired leakage, friction, and response time. Glyd Ring II seals reduce tolerance stack-up and its elastomer is bonded to the PTFE. In the final seal, the Variseal, the elastomer is replaced with a slant coil spring that energizes the seal, thus making sealing friction more consistent.