The conical centrifuge tubes include a convenient flat bottom so they stand on their own. The conical centrifuge tubes are made of virgin polypropylene. Easy-to-read black graduations are in 2.5 mL increments with a large black printed writing area. Smooth, flat surface plug seal caps for conical bottom tubes are included. The tubes are leak proof and withstands up to 6000 RCF. The tubes can withstand the temperatures -80°C. All tubes are Sterile, DNase, RNase, and Pyrogen free.