These 20mL vials are the original and the standard by which counting vials are judged. WHEATON 180" low-potassium glass (meets ASTM Type I Class A and USP Type I standards) and critical manufacturing tolerances ensure reliable, consistent results in scintillation counting. Vials load properly into counting machines without jamming or breaking. Background counts are consistent and low; ultraviolet transmission is high. White caps fit tightly to avoid solubilizer fumes in the laboratory and have tops suitable for marking. Dimensions: 28 mm x 61 mm