This is a custom re-programmable flash cartridge compatible with GB/GBC/GBA/Analogue Pocket systems. This flash cart works with both .gb and .gbc rom files. Specs: 8MiB Rom storage 256K FRAM Save (Forever Save) Works with MBC3 and MBC5 Chips Real Time Clock (RTC) Battery Type CR2032 (will work with CR2025) This flash cart will work with most of Game Boy games released. Check the gb game listing to determine if your rom is compatible with this flash cart. This flash cart is backward compatible with MBC1 chip. This cart uses Flash RAM for saves, so the save file will never be lost even when the battery dies. The battery is only for RTC, which should last 3-4 years. What's Included: 1 x Flash cart 1 x Cartridge Shell 1 x Plastic Case Will work with most flasher like GB Operator, GBxCart, or Joey Jr.