FWIW the picture above is for the DPMS 4 way kit not the Colt 4-way.
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Great info but mine is RDIAS, and I can’t get the 4 way sear.
Is it still going to work with my RDIAS with following 3 parts and obviously minus the 4 way sear?
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Yes should work with your RDIAS.
Oh and something I forgot to mention, you won't have to worry about this with a RDIAS, but those of us with a Register receiver do. For the RDIAS host receiver you will have to remove the selector stops. For those with a registered receiver. You need to cut the switch part off the selector and JB Weld a cut down cheap Selector switch on to it to be able to rotate it 360 degrees.
Edit to add:
There is a thread that is pinned/sticky in this section that pretty much covers all the questions about the 4-way
https://www.ar15.com/forums/Armory/M16-4-Way-Selector-Install/23-364516/