There are two main o-ring sizing types. Standard was developed for use in the USA, while the international community uses metric for their o-ring dimensions.
Seals Eastern - Flange Seal O-ring Design Guideline
Designing Axial Static O-ring Grooves to Industry Standards
O-Ring Groove Design Dovetail • Seal & Design, Inc
O-Ring Groove Design Global O-Ring and Seal
Browse all O-Ring Groove Design Guides - Marco Rubber
O-Ring Sizes And Dimensions • Seal & Design, Inc, o-ring
How to properly size an O-ring - UC Components, Inc.
Dynamic O-Ring Groove Design Guide – Rod and Piston Glands
O-Ring Groove Design Global O-Ring and Seal
O-Ring Sizes And Dimensions • Seal & Design, Inc, o-ring
O-Ring Groove Design Global O-Ring and Seal
Custom Large Size Natural Rubber Sealing O-Ring / Seal Gasket for Drain Pipe - China Cushion Gasket, Buffer Gasket
Backup Rings Global O-Ring and Seal
O-Ring Groove Design Global O-Ring and Seal