There are a huge amount of fake memory cards being sold on ebay. If you don't want to be scammed, test any you purchase to see if they work properly. You can also test any USB drives you purchase.
If you do a quick internet search, you can easily find what you need to test them, and how to use it.
Many people use Windows. I use Linux. You can install apps in either Windows or Linux or other operating systems, to test them. Anyone trying Linux for the first time, Linux Mint is the most popular. The Mate version is ideal for most computers.
In Linux you can install f3. You also need to install dependencies.
You can run f3probe, to test them. This will tell you if they are genuine or fake.
Another option is to run f3write then f3read, which writes to the entire drive, then reads from the entire drive to see if data is saved or lost, but this takes a long time.
If you don't want to do this, just copy files until it is nearly full, then see if any files are lost or corrupted.
The above tests the capacity of memory or USB drives, to see if they are genuine. There are some being sold which are the correct capacity, but lower speed than claimed. You can also test the speed.
In Linux Mint, an app for this is installed by default. This is called Disks. Select the drive, then Benchmark Disk.
