13 × 75mm tubes filled with buffered tri-sodium citrate solution 3.2 % (0.109 mol/L) concentration Mixing ratio is one part citrate to nine parts blood when tube is filled appropriately as indicated by fill mark on label Clear as glass with equal or better performance Molded to be virtually unbreakable, providing a better level of safety than glass 18-month shelf life from date of manufacture Blue nonscrew safety pull cap can be removed with a gentle pull