Buying a set of air fittings can be convenient. You can always find couplers and plugs at home centers and tool suppliers, but will it fit with your tools, air compressor, and other equipment?
A set gives you a variety of plugs and couplers, usually with both male and female threads.
Will you use all of them? Probably not. I find the convenience to outweigh the wastefulness and am okay having a couple of extra fittings around for when I need them.
Shown above is a Legacy ColorConnex set, with 1/4″ NPT threads and industrial Type D-style quick connect profile.
You can buy other fitting sets with other profiles – that’s where the color coding comes into play.
Picking up a kit means that all of your fittings will always be compatible, which might not be true if you’re not careful about mixing and matching couplers and plugs from different brands and suppliers.
Milton also has a similar set of color-coded industrial fittings.
Maybe you don’t need 14pc sets, in which case both brands have smaller assortments.
Legacy’s 5pc ColorConnext set is a cost-effective way to get started. It includes a female-threaded quick-release coupler, (3) male-threaded plugs, and (1) female-threaded plug, all 1/4″ NPT. This is enough to replace a hose-end coupler and standardize the connection across a couple of air tools.
The 5pc set is usually $9-10.