Due to its elasticity Snap Ring Caps are made out of Polyethylene. As the caps are pushed over the snap ring lips of the glass vial the cap is widened in diameter and then contracts, as the snap ring lips have been passed by, in order to guarantee an appropriate tightness. Up to now La-Pha-Pack® has only offered hard Snap Ring Caps, as their reset forces are stronger than those of soft snap ring caps and thus achieve a better seal. However, handling of the hard caps is more difficult, as they require a greater force to push on and off. Therefore the closure range has been enlarged by adding soft caps in blue and transparent colour. They can be obtained with different septa materials, including the new septa quality ”RedRubber/PTFE“, a cost-effective synthetic rubber that is easy to penetrate and that has a sufficient analytical purity for routine analyses. Another new and innovative product for chromatography are Snap Ring closures with pre-cut septa where only the Silicone layer is slitted while the chemical inert PTFE lamination remains intact. Thus you have a septum that fulfils the requirements of the needle for a penetration aid without showing the problems of completely slitted septa. These are concentration changes due to evaporation of solvents as well as contamination due to extraction of volatile substances from the Silicone material.