The Revo K101 Plus is a Game Boy Advance clone that can run physical cartridges. What made it renowned among the clone community is its ability to play GBA ROMs on a special cartridge supplied with the console.
The K-card is the name of the special cartridge. Although it isn't a technically isn't a flash card because it doesn't work on real Game Boy Advance consoles, it works exactly like one. In addition, it runs Nintendo Entertainment System, Sega Master System, Game Boy and Game Boy Color ROMs, though NES games have distorted audio and sometimes visuals are very blocky. Master System games run significantly slower.
Along with ROMs, it allows playing of MP3 files, text file readers, a real time clock, a JPG viewer, and ability to set boot screens and backgrounds. If using physical cartridges, it functions that same as any Game Boy Advance console.
The K101 Pro is a knock-off of the Revo K101 Plus. It also goes under the name of CoolBoy RS-97 and the Retro Game.