I believe there are 2 separate versions for GBB and AEG for the Magpul PTS UBR. Maybe you got the wrong one?
If you check the first picture in this thread, the buffer tube at the very top is for GBB. The smaller tube and screw below it is for AEG. the tube looking thing on the right is actually not a tube but a different cheekrest you can install. If you got a threaded buffer tube that screws in the like the very top one, thats the GBB version.
Last edited by jamex; May 24th, 2012 at 15:48..
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