O-Ring and Internal Thread Sterile Certified DNAse, RNAse, pyrogen, and DNA-free. Both cap and tube made of polypropylene; ensures secure seal at all temperatures Super fast 1 ¼ turn thread design Virtually unbreakable Graduated with large white marking area Excellent clarity makes sample easy to see Packaged in tamper-proof, resealable bags Colored cap inserts available in multiple colors Bag of 100 cryovials