Premium Quality: This assortment features high-quality HNBR (Hydrogenated Nitrile Butadiene Rubber) O-rings, known for their excellent durability and resistance to heat, oil, and chemicals. Ideal for R134A Air Conditioning Systems: Specifically designed for use in R134A air conditioning systems, ensuring reliable performance and a secure seal. Comprehensive Size Selection: Contains the 18 most popular sizes to meet various sealing needs, including: 7/32? x 1/16? – 20 Pieces 11/16? x 5/64? – 10 Pieces 1/4? x 1/16? – 20 Pieces 7/16? x 5/64? – 15 Pieces 9/32? x 5/64? – 20 Pieces 7/16? x 3/32? – 15 Pieces 5/16? x 1/16? – 20 Pieces 1/2? x 5/64? – 15 Pieces 5/16? x 5/64? – 20 Pieces 9/16? x 1/16? – 10 Pieces 5/16? x 5/64? – 20 Pieces 9/16? x 3/32? – 10 Pieces 11/32? x 5/64? – 20 Pieces 5/8? x 5/64? – 10 Pieces 3/8? x 5/64? – 10 Pieces 11/16? x 1/16? – 10 Pieces 7/16? x 1/16? – 15 Pieces 11/16? x 1/8? – 10 Pieces Convenient Packaging: Organized in a durable storage case for easy access and organization. Perfect for automotive and HVAC applications, this 270-piece HNBR O-ring assortment ensures you have the right size on hand for all your sealing needs.