A "no additive glass tube" could imply that the glass is made using only the basic ingredients without any additional substances. This might be desirable in certain applications where purity or specific material properties are important, such as in scientific experiments, laboratory equipment, or in industries where any impurities could affect the end product. Convenient handling of sample with a capacity of 3 mL / 4 mL / 5 mL allowing for flexibility in blood sample storage and transportation.