The best TBB's on the market are either the DB custom, EDGI, or PDI barrels. All three run above $70 if you can get your hands on them.
The next best IMO are Prometheus, and KM head barrels.
The lowest, but not bad TBB's are Systema, and Madbull. I have been impressed by both of these brand barrels, and if you polish them well they will perform just as well as a Prommy or KM head barrel. Heck even better if you use good BB's.
The only barrel that you cannot use on all AEG's are the M14 barrels. They have different nubbing cuts in them. Besides that all I would do is match the cylinder too your correct barrel length.
sticks