Understanding and Identifying the Body Size of ISO A and ISO B Quick Couplings


When it comes to replacing quick disconnect couplings, knowing how to correctly identify the type and body size is crucial. This guide will help you understand ISO A and ISO B quick couplings, and how to determine their body size to ensure you find the right replacement for your equipment.

What are ISO A and ISO B Quick Couplings?

ISO A and ISO B are the Series A and Series B in the international standards of ISO 7241 for hydraulic quick disconnect couplings. These couplings are widely used in various industries, including agriculture, construction, and manufacturing. Each type has distinct features and applications:

ISO A (ISO 7241-1 A)

In the ISO 7241-1 standard , they specified the interface dimensions and basic performance requirements for two series of hydraulic quick couplings. The Series A, we called them ISO A quick couplings, which is used predominantly in Europe and is preferred worldwide for agriclutural and forestry machinery. In the ISO 7241-1 standard document, it also specifies addtional requirements for Series A for use in the agricultural machinery applications given in ISO 5675. So, the ISO 5675 is based on ISO 7241 Series A.

ISO B (ISO 7241-1 B)

The Series B is used perdominantly in North America and in the chemical industry. It is mentioned in the document of ISO 7241. Nowaday, they can be found in lots of industries, ncluding agriculture, construction, and manufacturing.

Steps to Identify the Body Size

Identifying the body size of ISO A and ISO B quick couplings involves measuring and understanding the key dimensions of the couplings.

Check for Identification Marks

Many couplings have size and standard markings engraved on them. Look for any numbers or letters that indicate the size and type.

Different manufacturers have different product number naming rules. For example, Parker 6600 Series is Parker’s ISO A quick Coupling Series. In their catalog, you can find the part number 6601-4-4, which corresponds to female coupler, 1/4″ body size, and 1/4-18 NPTF Thread. The corresponding product should have the mark 6601-4-4. Similarly, you can find the corresponding IA-6, 3 F NPT1/4 in our IA series catalog. These two products are interchangeable.

Measure the Diameter

In the ISO 7241 standard document, we can see that the document specifies a series of dimensional requirments. The dimensions are mainly on the male coupler. Therefore, we can usually judge the quick coupling type and size by the key dimensions of the male coupler.

Differences on ISO A and ISO B quick couplings 1024x256 1
Body SizeISO A Diameter(mm)ISO B Diameter (mm)
6.3 (1/4″)11,73-11,8614,1-14,2

Roughly judge ISO A and ISO B Couplings

This method is difficult for novices. But for users who often come into contact with quick couplings, the type of quick couplings can be judged by the length of the first step of the male coupler. There is a more obvious difference between ISO A and ISO B. In the case of the same body size, the length of the first step of ISO B will be longer.


In the image above, they are both 1/2″ body size, the ISO B coupler left, the first step length usually longer than ISO A. And usually in same body size, the ISO B would be heavier and looks stronger than ISO A couplers.


ISO A and ISO B have similar structures and are two types of quick connectors specified in ISO 7241 standard. Their uses are also similar. We can identify them by key dimensions. ISO B is made of stronger materials and has a longer connection stroke.

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