Aijiren Technologies. 20mm Headspace Crimp Caps without Septa (2715F74, F77) For use with all headspace crimp top vials. Caps with safety feature release at approximately 45 psi. 20mm Headspace Crimp Caps with Septa (2714S39 to S42) Pre-assembled 20mm crimp caps with septa. Ready-to-use with any headspace crimp top. Compare this item.