High quality: in nitrile rubber (NBR).High resilience and high resistance.Not easy to dotear.It's not pollution or an odor.Durable and long life. 18 sizes: The kit includes the most commonly used O-rings on the market.: 3x1mm, 4x1mm, 4.5x2mm, 5x2mm, 6x2mm, 6x2.5mm, 6x3mm, 7x2mm, 8*2mm (20 each);9x2mm, 10x2mm, 12x3mm, 13x3mm, 14x2.5mm, 17x2.5mm, 18x4mm, 20x2mm, 22x2mm (5 pieces each). Easy to useUse: Soft, flexible O-rings only need to be snapped into place and are easy to remove.install.They are very suitable for sealing gasoline, diesel, lubricating oil, water, air, gasoline and various chemicals. Convenient Box: Durable independent space can keep O-rings separated to avoid confusion.And easy to use.carry. Wide range of uses: suitable forplumbing,automotive repair, air conditioning manifolds, garages, workshops, automobiles, doors and windows, household appliances, bearings, pumps, pulleys, etc.