1st hydrolytic class glass 51 expansion autosampler glass vials snap top-HPLC Autosampler Vials. The vials are made from 1st hydrolytic class 51 expansion glass which, unlike inferior alternatives, allows the manufacturing of clean, precision-fit vials. Our comprehensive range of vials includes micro and fused inserts, standard 2 mL autosampler and larger sample storage, glass sample vials with screw caps, headspace vials, and EPA vials.