SD cards should not be used in an MMC card socket.
SD (Secure Digital) memory cards use slightly different technology and are physically slightly thicker than MMC (Multi Media Card) memory cards. You cannot use an SD card in an MMC card socket.
Background
Various technologies have been developed for the popular memory cards commonly used in digital cameras, mobile phones and other portable devices. You should identify which technology your mobile devices use and purchase the correct cards for your needs.
Compatibility
SD and MMC cards look very similar but are not completely compatible. The thinner MMC cards will often work in an SD card socket, but the thicker SD cards will not work in an MMC socket.
Suggestion
It is possible to purchase card readers with multiple slots that allow you to read all common memory cards, ensuring that all cards can be read by your PC or laptop. Modern PCs sometimes come with these card readers already integrated.
Tags: memory cards, card socket, card readers, cards will