Game development kits (GDK) are specialized hardware and software used to create commercial video games for game consoles. They may be partnered with game development tools, special game engine licenses, and other middleware to aid video game development. GDKs are typically not available to the public, and require game developers to enter an agreement, partnership, or program with the hardware manufacturer to gain access to the hardware. As console generations pass, development kits often get sold through websites like eBay without repercussions. This is often because the console manufacturers discontinue certain development programs as time passes.