We find the ones with the teflon lid liners to be the most durable for our resists. On Oct 31, 2005, at 7:04 PM, William Lanford-Crick wrote: > . Can someone > recommend which is the best cap material for our applications? > Options are: Poly-Seal*-lined Closures, Polyvinyl-lined > Closures, > Rubber-lined Closures, or Teflon* Faced PE-lined Closures.