These tubes reduce changes in pH and potential contaminants from tubes that are made from soda lime glass. They have round bottoms and feature fire-polished smooth rims. Chemically inert, suitable for use in blood banks and tissue culture. Made in an ISO 9001:2008 certified factory, they are packaged well in heavy duty boxes and shrink-wrapped to stay particle free. The boxes will fit neatly into most test tube dispensers. The tubes are available in 8 sizes.