Everdrives are the top of the line flashcarts for various retro systems. They allow you to boot roms and romhacks on original hardware without any modification required. For each system, there are various price levels that give extra features. For example, the GB X7 provides a rtc (aka Pokemon games keep time) but is more expensive. The only sale they typically do during the year is Black Friday event.

From everdrivestore.com, "What is an Everdrive?":

An Everdrive is a flash cartridge that allows you to play games on your console. The cartridge is easy to use. You “drag and drop” files from your computer onto a * micro SD card that you insert into the Everdrive. When you turn on your console, a list of games will appear. With your controller, you select the title, and you're done!