Borosilicate glass KIMAX™ -51 composition assures all-around chemical durability of commercial glasses now available for laboratory ware. Complies with ASTM Specification E438, Type I, Class B glass requirements. KIMAX™ -51 has excellent chemical resistance against sodium leaching—a factor common in soda lime glass products. These are premium quality tubes with sturdy, uniform bottoms and consistent lengths. Trays are shrink-wrapped in plastic film with tubes remaining in constant alignment for protection against in-transit breakage and contamination. Designed from ASTM Specification E890.