Quick couplers on air brake system

What is a M style coupler?

 

I have used the prevost couplers on my but they dont handle dirt as well as the miltons used them for my air pressure guage in cab for the trailer. And the miltons u want to use for airline conectors is the g series they are alot bigger then m series the gs are for 1/2 and 3/4 inch hoses and m series generally for 3/8 hoses.

 

Extremely great advice. Do I switch to 1/2 inch hose? My glad hand hoses are 3/8 rubber hose. Yet, the truck and trailer hoses are plastic. I will check the size on the plastic hose as they very well may be 1/2. Thank you.