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Hydraulic Boss O-Rings

Hydraulic Boss O-Rings for use with Hydraulic tube fittings.

There is 20 standard sizes for O-rings used to seal straight-thread tube fittings on a boss. A boss Tube fitting with boss seal is cylindrical projection on a casting or forging. The end of that projection is machined to provide a flat, smooth surface for sealing. Straight threads used with an O-ring provide a better seal than tapered threads used alone. Although made in a variety of o-ring compounds the most common Boss O-rings are Buna-N in 90 Durometer.

The 900 series of dash numbers identifies the 20 sizes of boss seals. Except for size -901, the digits after the 9 identify the nominal tube size in 16ths of an inch. The tube size is its outside diameter (OD). For example, size -903 is intended for use with 3/16-inch tube. The one exception, size -901, is intended for use with 3/32-inch tube. 1/16-inch tube is not common in aircraft use.

We started as a simple online company taking care of a precious few people. Our circle of business friends has grown over the years and taking care of them is more satisfying than ever. We take care of our customers' Standard O-Rings, Metric O-Rings, Vulcanized O-Rings, and Custom O-Rings. Just place your O-Ring order online and we will take care of you too.

We are a family owned and operated Distributor and Manufacturer of O-Rings, O-Ring Kits, OSK™ O-Ring Service Kits, Hydraulic Seals, Adhesives, Lubricants, Braided Packings, Coatings, O-Ring Cord, Lathe Cut, Oil and Shaft Seals, Gaskets, Retaining Rings, Molded Packings, Seals, and Molded Rubber Products.

We serve many industries, including manufacturing, chemical processing, defense, power generation, agricultural, water treatment and filtration, hydraulics, fluid power, heavy truck, automotive, aerospace, oil and gas, medical and life sciences, food and beverage, electronics and industrial controls, refineries, and supply chain suppliers. Each industry and each customer have unique requirements that make them special. We love sharing customer stories and applications at our weekly store meeting.