Kimble Disposable Glass Culture Tubes are manufactured of KIMAX-51 borosilicate glass in compliance with ASTM specifications, and feature sturdy, uniform bottoms, and consistent lengths. Glass culture tube composition assures the best all-around chemical durability of commercial glasses now available for laboratory ware. Lipless tubes can use plugs or stoppers; screw thread tubes have GPI threads for autoclavable black phenolic caps, available separately. Some tubes listed have a white, chevron shaped writing area to allow for easy tube identification. Tubes are packaged in convenient, modular trays for ease of use on bench tops and in drawers. Trays are shrink-wrapped in plastic film, keeping glass culture tubes in constant alignment for protection against in-transit breakage and contamination. Key Features Borosilicate glass KIMAX-51 with round bottoms provides the best all-around chemical durability of commercial glasses Plain-neck lipless tube can use plugs or stoppers Screw-neck tubes have GPI threads for autoclavable black phenolic caps Tubes are packed in convenient modular trays for ease of use on bench tops and in drawers