Heavy wall glass storage bottles with #15 Ace-Thred are intended only for storage of low-boiling liquids at room temps or at not less than -20 degrees C. Designed to resist internal pressures up to 100 psi, as low as -20 degreeC. The low pressure rating based primarily on the rating for PTFE T.F.E. Safety coated to the neck to help prevent shattering and reduce spills.Closures are inert PTFE plugs with FETFE O-tings that will not freeze. 2 closure styles: with O-ring positioned at the front of the thread or with O-ring at the top of the thread.