Always check the warranty period. Most reputable dealers offer 30 to 90 days.

Many amp manufacturers (Mesa/Boogie, Fender, Marshall) sell tubes under their own brand name. These are usually just rebranded tubes from major factories (like JJ or Shuguang), but they have been specifically tested to meet the fixed-bias requirements of those specific amps. If you own a Mesa and don't want to worry about biasing, buying is a safe, plug-and-play move. What to Look for Before Buying:

A legendary name in the NOS world. His site looks like it’s from 1995, but his knowledge and inventory of vintage glass are world-class.

If you need a standard set of JJ or Electro-Harmonix tubes quickly, the big-box retailers are reliable and often have the best shipping rates.

Ensure the seller offers "matched pairs" or "matched quads" for power tubes. This ensures your amp runs efficiently and sounds balanced.