Made of high quality 100% pure virgin medical grade polypropylene so you won’t find recycled plastics in our tips. Every lot is lab tested and certified free of detectable Nuclease (Rnase/Dnase), Endotoxin (pyrogen) contamination, and certified to U.S.P. results. Resins are pre-tested for metal contamination. All our tips in racks are packed in teal racks. These racks are made of polypropylene and are autoclavable repeatedly. They have sturdy latch hinges that won’t come apart like lesser quality tip racks and a special snap lock designed so that it will not catch on your gloves.