I've bought myself an EZ-Flash II flash cartridge for the Gameboy Advance for £15. It was honestly a bit of an impulse buy, as I was pretty curious about it. The listing showed a game cartridge, along with some sort of cartridge dumper, which is what really got me interested enough to send an offer.
My specific cartridge, the EZ-Cart 128Mb, has a production date of 09/2003, making it about as old as my rusty shitheap of a car. As you can probably imagine, getting this to work on anything modern is a challenge, as the drivers seem to only work correctly on Windows 98 (for me at least.) The drivers are unsigned, and 32-bit, so forget about running this on Windows 10. Linux support seems to be non-existent as well. Luckily, I have a hoard of old Thinkpads, and my trusty X24 laptop works great with the flasher.
The cartridge has a capacity of 128Mb. Sounds impressive, until you remember the difference between megabytes and mebibytes. 128Mb is equal to 16MB, which means that the cart will fit a grand total of ~2 games, depending on the size of your ROMs. I imagine that for the time this was alright (I was 2-3 at the time) however I have been spoilt with my more modern EZ-Flash Omega, with support for SDXC cards up to 128GB. A cartridge with the entire GBA library on it would've literally blown people's minds I bet.
Finding the software really isn't a challenge, searching the cart's name leads you to a few forum posts with links. However that can always change, so I have uploaded the latest EZ Client to this website, click here to download. The drivers are inside the install directory. Inside there you will also find a .mhtml file describing how to manually install drivers from an .inf file, if you don't know how to do that.
The flasher also has the bonus feature of being able to read and dump GBA carts. I would have loved for it to support GB/GBC games too, however it is understandable why they didn't add support due to the voltage differences between the two systems (GBA uses 3.3V logic, whereas the GB/GBC uses 5V.) I have found a Japanese website that describes a modification that can be done to the flasher, and I may give it a go one day. I will keep you all updated if I ever do.
This cart is actually pretty good. It loads games instantly, as unlike the SD card based flashcarts, there is no need to write anything from the SD card to the GBA-readable EEPROM chip, as you already flash the game onto the EEPROM with your PC. Games also save perfectly fine, which is something that cheaper modern cartridges have trouble with (looking at you, Supercard...) My cartridge is only 128Mb, however they made carts up to 1Gb, which should fit a decent amount of games.
If you ever see one for a good price, it's a nice little oddity to mess around with. It's not something I would shell out a huge amount of money for though, if you just want to dump GBA/GBC/GB games then there are way better dumpers and flashers all over AliExpress and eBay. Even though I have way better ways to play muh vidya, there's something charming about using period correct kit like this.
EZ Client 3.26 software and drivers