Polyethylene (PE) flanged plug caps provides exceptional leak-resistance in test tubes, centrifuge tubes and round cuvettes. They feature two flexible flanges that press firmly against the inside wall of the tubes, thereby providing better leak-resistance than standard plug caps. The caps are available in a 12mm, 13mm and 16mm sizes and in 9 beautiful colors for sample identification purposes. Packaging: 1000 per bag. This listing is for 1000/Bag.