Our precision molded centrifuge tubes are made with extra thick, uniform walls so that they can withstand continuous spinning at 1800 RCF. The tubes are constructed of either crystal clear polystyrene or auto-clavable polypropylene. The tubes have graduations at 1/4, 1/2, 1, 2.5, 5, 10, 12, and 15ml molded into the wall. Blue polyethyl-ene plug caps will seal tubes for storage and transport. Leak proof sealing ring design assures proper sealing. Ribbed cap edge makes it easy to remove caps even if your hands are wet. Tubes are in bulk packs of 1000 tubes.