High Quality: Made of nitrile rubber(NBR). High Resilience and High Tensile Strength. Not easy torn apart. It is no pollution and no abnormal smell. Durable and long service life. 18 Sizes: Kit includes a variety of the most used o-rings on the market : 3x1 mm, 4x1 mm, 4.5x2 mm, 5x2 mm, 6x2 mm, 6x2.5 mm, 6x3mm, 7x2mm, 8*2mm (each 20pcs); 9x2mm, 10x2mm, 12x3mm, 13x3mm, 14x2.5mm, 17x2.5mm, 18x4mm, 20x2mm, 22x2mm (each 5 pcs). Easy To Use: Soft and flexible o ring, simply snap on, easy to install, great for sealing gasoline, diesel oil, lubricating oil, water, air, gas and various chemical. Handy Case: Durable separeted space keep O rings to separate, prevent them mixed up. And easy carry. Wide Usage: Great for plumbing and auto repair, A/C manifold, garages, workshops, cars, doors, windows, appliances, bearings, pumps, pulleys, etc