ILMs have differently placed protrusions which are intended to mate with cutouts in CPU packagings. These protrusions, also known as ILM keying, have the purpose of preventing installation of incompatible CPUs into otherwise physically compatible sockets, and preventing ILMs to be mounted with a 180-degree rotation relative to the CPU socket.

Different variants (or generations) of the LGA 2011 socket and associated CPUs come with different ILM keying, which makes it possible to install CPUs only into generation-matching sockets.