These glass vials are made from high-quality, thick borosilicate glass. The diameter was specifically designed to fit in the Flystuff Reload Trays (59-207XXX). The light glazing around the edge provides a straight wall design for the tightest closure fit. All glass vials are conveniently packed in a 180/tray formation with cardboard dividers. These vials are available by the tray or by the case.