That's for a rifle tube anyway, right?
Are there differences in rifle tubes? I know there are in carbine tubes but don't think there are in rifle tubes.
Did you try it and it does not fit?
If it's for a carbine tube somehow, you can get a new carbine tube. BUT you probably can't replace the tube on your duty rifle- some places won't allow changes that require tools or an armorer.
Magpul makes the CTR stock for commercial or milspec tubes.
But, it definitely isn't the Vltor you ordered.