Sarstedt Stopper, Tubes, For 13 mm Tube, Polyethylene, 10000 Count. These push caps for tubes are constructed from low-density polyethylene (LDPE), a material renowned for its exceptional flexibility and robust resistance to a wide array of chemicals, including acids. Each bag contains 1,000 white stoppers, making this a convenient and cost-effective solution for your laboratory needs, with a total of 10,000 stoppers provided.