Serum Vials and Closures. Thermo Scientific™ Nalgene™ PETG Serum Vials with Crimp Finish: Nonsterile, Shrink-Wrapped Modules. Protect against leakage, breakage, and contamination. Nalgene PETG Crimp Finish Serum Vials are lighter in weight than glass, and are made for use with stoppers and caps. Pricing and Availability.