An NFPA Tie Rod Cylinder Primer
The National Fluid Power Association (NFPA) has created standards regarding Pneumatic and Hydraulic cylinders. Often referred to as tie rod or NFPA cylinders, they are the commonly used workhorses in industrial machinery. They are rebuildable and come in varying duty ratings. The standards published by the NFPA dictate specific mounting styles and dimensions to ensure compatibility and performance across manufacturers.
These standards are available for purchase, but it is generally easier to refer to a manufaturer's catalog for standard NFPA options if that is what you need. Unfortunately, even though dimensions and mounting styles are standardized, the naming and numbering conventions can vary by manufacturer. It is navigable, but usually a pain to cross-reference. Inner parts, such as seals and pistons, may not be interchangable between manufacturers.