Corning tubes are available with either plug seal or flat top caps. Fifteen- and 50-ml tubes feature black printed graduations and a white writing patch; 250- and 500-mL tubes feature molded-in graduations. All are sterile and certified Nonpyrogenic. The 50-ml tube 17400-44 is self-standing. You can color Code the 15- and 50-ml plug seal tubes using the cap inserts sold separately on page 163. The 250- and 500-mL tubes require adapters 17404-00 and 17404-05 respectively, sold separately.