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2) Mil spec CTR may fit or may not fit. But PTW stock tube is between mil spec and commerial size. Commerical guarantee will work, but might be a little bit wobble. So I think the best way is use mil-spec CTR and sand down the inside a little bit in order to get a tight fit on your buffer tube.
3) UBR PTS aeg version will not fit. Gbb version, may be.

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That's what I think, but I am so surprise my ACS Mil spec can fit on directly, even though it's a little bit tight. On the other hand, my CTR Mil spec can't fit on directly. QC problem?? .

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No, RS ACS mil-spec version. To be honest, I will still go with mil-spec no matter what, since commerical is too loose for PTW buffer tube. It won't give you a tight fit, and the stock will wobble.