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.