Open Top Sample Vials In Lab File. DWK Life Sciences (Wheaton) Clear or amber 20 mL capacity 24-400 screw cap Clear vials are manufactured from Wheaton 33 low extractable borosilicate glass that meets ASTM Type 1 Class A and USP Type 1 standards. Amber vials are manufactured from Wheaton 320 amber glass that meets ASTM Type 1 Class B and USP.