I'm aware of at least three versions of the Prevost S1 couplers: industrial, truflate and high-flow. They're color-coded: blue button is industrial, red button is truflate, green button is high-flow. Most will want the industrial ones for home use since that's the most common coupling (i.e. the one you can find at the local hardware store on a Sunday). But if you're just starting out, it may be worth buying a pile of the high-flow parts so you can readily outfit new tools as you buy them And one or two extras to build adapters for those times you need to use someone else's hose setup.
I like the original Prevost safety couplers (ISC 06 and ISC 08) and have been hoarding the ones I have because few are carrying them now. I've had them for so long that it's become habit for me to release the air pressure from a tool while still having it attached to the hose. It's a great feature for any palm-switched air tools, especially those you want to set down on their palm switch to avoid contamination (for example, I use Dynabrades for polishing and waxing the cars and don't want contaminants on my pads). I also find them handy when holstering a nailer set up for bump nailing and just for general safety around the garage. The S1 couplers are hence a big disappointment to me and I've bought the Milton safety couplers recently. Having a hose connected but no pressure is just great when you need to move from one area to another without air pressure to the tool but still having the coupler connected so the hose still follows the tool.
They're not cheap, but they last a very long time. I still have my first Prevost safety coupler in regular use (it's on the most-often used hose reel) and it continues to work flawlessly. I can't remember when I bought it, it was a very long time ago (10 years?).
