Excellent solution - FAB Defense AR-15 Survival Buttstock w/Built-in Mag Carrier

I bought mine on ebay, directly from FAB, and received it in 2 days.

It fits fine on my milspec tube. I think those who complain maybe don't know how to install an AR stock. There is a hole in the top of the stock, above the locking pin. You need to push and hold that pin ALL THE WAY DOWN with a screwdriver in order to fit the stock onto your tube. This is what will keep the stock from coming off the tube when you extend it all the way.

The is friction on my milspec tube, so it takes a little force to adjust the stock, but nothing extreme. The 10rd plastic mag that comes with the stock slides in and out easily. There is more friction with my 20rd GI mags, which is fine, but not what I would have guessed.

Overall I think this is a great solution for a backup mag or for carrying you rifle with ammo, but not loaded. It works great with the included 10rd mag or even with a 20rd. A 30rd mag would probably extend too far to be practical.