Quoted:
I currently have a 6 position stock and I want switch it
out with a 4 position do I have to change the tube also?
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There is a 2-position, 4-position and 6-position tube .etc but the stock doesn't dictate the positions
In addition to the number of positions, extension tubes have 2 sizes that will determine what collapsible stocks will fit on them. Commercial and Mil-Spec diameters.
If your stock and tube are both commercial it will work
If they are both mil-spec it will work.
A commercial stock will fit on a mil-spec tube but will have a lot of play. A mil-spec stock will not fit on a commercial tube.
You don't have to change out the tube if the diameters match, though you may find the extension tube protrudes in the forward setting.
I actually preferred this as I used the protrusion to stand mine up as a lamp.