MDE 86 is correct.
They are essentially the same shaft. The pro series shafts are graded for .001and w/i +/- 1g, where as the xt are graded at .003 and w/i +/- 2g. Basically you pay a premium for consistancy. IMO the less variables there are, the more consistant your shooting will be. For what I spend on archery, spending $100.00 (on IMO the best shafts on the market) is money well spent.

Just my $0.02 on the GT pro shafts.