From top to bottom:
Standard carbine buffer tube
Vltor A5 – Ignore the rough look.   It has Acraglas on it to give it a snug fit for a specific collapsible stock.

Vltor A5 is right at about 7 – 11/16″

Hard to tell from the camera angle but the PSA PA-10 tube is the same.  This has milspec threads and any standard AR carbine stock works on this buffer tube…just like an A5.  It does have 6 position vs 7 like the A5 but I’m fine with that.

Standard carbine tube is 7″ for comparison.