The Performance Tool W5201 270-Piece HNBR O-Ring Assortment provides a wide range of o-ring sizes for various applications. Made of hydrogenated nitrile butadiene, these o-rings offer higher resistance to chemicals and temperatures than standard NBR materials, while also being abrasion-resistant for demanding applications. The set comes in a convenient organizing case with labeled compartments for easy identification and storage of o-rings, making it ideal for use in vehicle and tool repair, plumbing, hydraulic applications, and more.