Snap Cap Vials are an extension of the crimp cap system of sealing. A plastic cap is stretched over the rim of the vial to form a seal by squeezing the septum between the glass and the stretched plastic cap. Plastic has memory and wants to return to the original dimension. This tension in the cap to return to its original size is the force forming the seal between glass, cap and septum. The advantage of a plastic snap cap is no tools are required to assemble. The snap-top cap is a compromise sealing system.
