Nalgene Unwire These durable, brightly colored racks feature a three-tier design Racks for 13mm and 16mm tubes hold 72 tubes; racks for 20mm and 25mm tubes hold 40 tubes; racks for 30mm tubes holds 24 tubes. Autoclavable. They have excellent chemical resistance and can be immersed in a water bath. Letters and numbers on top tier aid in tube identification. Labels can be placed on large end plates. ResMer technology allows these racks to be used over a wide temperature range.