SIBATA Plastic Base, To Contain, Student Grade Glass Graduated Cylinders meet ASTM E-1272 Class B, Style I Specifications for Classification and Tolerances. These cylinders are made of two parts: a strong, accurate glass graduate and a detachable, sturdy, plastic hexagonal base which absorbs impacts and reduces breakage. Feature hexagonal bases for added stability. All cylinders come with protective, polyethylene, hexagonal bumper guards. All markings are in durable, white enamel.