These vials provide low and consistent background counts and have high ultraviolet transmission. Precise manufacturing tolerances ensure dependable and consistent performance for scintillation counting; the vials load smoothly into counting machines without the risk of jamming or breaking. Vials are madefrom borosilicate glass that meets ASTM Type I, Class A, and USP Type I standards. Included white caps fit securely and can be labeled for easy sample identification.