DuoClick™ Two Position Screw-Cap Plastic Culture Tubes feature a unique screw closure system. DuoClick™ tubes completely eliminate the excess force, splashing and general frustration of traditional snap-cap culture tubes. The advanced cap design includes two distinct positions for aerobic and anaerobic culturing. Just rotate the cap 1/4 turn to the first click to secure the cap in the aerobic position. Or, rotate it another 1/2 turn past the second click for a leakproof, airtight seal for anaerobic culturing. DuoClick™ tubes are available gamma sterilized, with screw caps attached, and in our exclusive ready-to- use rack packaging. Polypropylene tubes can be centrifuged at up to 4,000xg. Aerobic culturing at first click. Anaerobic after second click. They have printed graduations witth flat, markable screw-cap.