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.
AS568 Standard O-Rings (Inch)Metric O-Rings - Standard and ISO 3601OSK™ Assorted O-Ring Kits ↪ Buna-N 70 O-Ring Kit ↪ Buna-N 90 O-Ring Kit ↪ Aflas O-Ring Kit ↪ Automotive O-Ring Kit ↪ Back-Up Ring Kit ↪ Boss O-Ring Kit ↪ Buna-N 50 O-Ring Kit ↪ Caterpillar Compatible O-Ring Kit ↪ EPDM O-Ring Kit ↪ Face Seals ↪ FDA Grade O-Ring Kits ↪ Flange Kits ↪ HNBR Green O-Ring Kit ↪ Metric O-Ring Kit ↪ Neoprene O-Ring Kit ↪ OSK™ CV75 Extreme Chemical Resistant FKM O-Ring Kits Black ↪ OSK™ FKM (Fluorocarbon) O-Ring Kits Black 90 Duro ↪ OSK™ FKM/Viton (Fluorocarbon) O-Ring Kits ↪ OSK™ Max Truck O-Ring Kits ↪ OSK™ X-Ring Kits ↪ Paintball & Air Rifle Kits ↪ Plumbing O-Ring Kit ↪ Pressure Washer Kits ↪ PTFE Temperature & Chemical Resistant O-Ring Kits ↪ Silicone O-Ring Kit ↪ Square O-Ring Kits ↪ Urethane O-Ring KitHydraulic Seals - InchHydraulic Seals - MetricO-Ring Cord StockO-Ring Glue & Thread SealantO-Ring Lubrication ProductsO-Ring Splice KitsOil Seals - Shaft SealsOlypsys™ for O-RingsOSK Pool, Spa & Pump O-ringsOSK™ Air Nailer O-Ring KitsOSK™ Hydraulic Cylinder Seal KitsOSK™ O-Ring Repair KitsOSK™ Spray Foam O-Rings for Graco® and PMCVulcanized O-RingsContinuously Molded O-RingsOSK™ OEM Replacement O-RingsOSK™ Custom O-Rings & KitsSpecials ...Featured Products ...
AS568 O-Ring Information O-Ring Back-Up Ring Sizes O-Ring Elastomers ® Site-Wide Trademark List Metric O-Ring Information ASTM Specifications O-Ring Groove Information O-Ring Size Chart PDF O-Ring Cord Information Hydraulic Seal Information O-ring Temperature Chart O-Ring Shelf Life RoHS & REACH Info Quality Standards Manual O-Ring Industries Served O-Ring Store Links