I don't know about AR15's except that I wish I had bought one when I would have been able to enjoy it.
I bought some items from Combat Armory and was very satisfied with their product and service. I get their sale stuff on my computer and this one looked very interesting for AR15 people;
Magpul Matrix Complete MOE Kit $69 and free shipping.

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Mighty 90's,Trying 4 a 100!