The Memory Stick Duo was introduced in 2002 by Sony to meet the need for smaller memory cards for pocket digital cameras, mobile phones and the PlayStation Portable.
The Memory Stick PRO Duo replaced the Memory Stick Duo due to its 128 MB size limitation, but has kept the same form factor as the Duo.
The Memory Stick PRO-HG Duo, released in 2006, achieves three times the speed of the PRO.
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