In pneumatic systems, there are two main types of air couplings:

Industrial Interchange Couplings (Type "M" and Type "T")
Universal (or European) Interchange Couplings (Type "A" and Type "E")

Although the design and profile of these two different types of air couplings differ, they are both used to connect compressed air to pneumatic tools, hoses, and other equipment. To prevent leaks or other issues, it is crucial to ensure compatibility between the couplings and the pneumatic system components.