I have dealt with an aircraft supply shop for years without problem and the materials are top quality. Whenever i have to get an 'odd' piece of something i go local and the crap i get from them is incredible.
The telling difference between quality aqnd junk is when i machine or drill it. If i run a drill bit into good milspec chrome moly the cuttings off the bit are consistant and even, the drill bit penetrates in a smooth motion and the resistance is the same all the way thru. With commercial grade metal the cuttings fly off the bit in inconsistant chips, the bit penetrates haphazardly and you have to push it thru rather than it cutting thru.