Grades A, B & C. And the sneaky, Grade D
Tier 1 OEM flash chips. These are made by the same legitimate chip manufacturers in Grade A but are without the manufacturer's brand name imprinted on them. These chips are as reliable but may not be of the same standards that the manufacturer would consider putting their name on it. Kennedy Advertising also sells Grade B. A and B are both fine to use.
These are called recycled or reclaimed flash chips (not to be confused with the recycled plastic housings) . These chips are considered waste from the "wafer" that the original manufacturer does not want and considers to be garbage. These have a 30% - 40% failure rate. They are sold by the pound. Literally!!!
A Sneaky flash drive supplier will actually imprint an original manufacturer's name on a Grade C chip. It may say Samsung or Hynix, etc. but its most definitely junk/knock-off flash drive. Until The Sneaky Grade Flash Drive land’s at your customer’s door you will not know that they don't work very well.