Oyen Digital 2-Port ExpressCard SuperSpeed USB 3.0 Express Card Adapter for Mac Supports Express Card/34mm slot on MacBook Pro 15" or 17" (with ExpressCard slot). The card is NOT compatible with the 2011 17" MacBook Pro models. Requires Mac OS X Version 10.6 to 10.8.5 (NOT compatible with OS X 10.9 Mavericks) Not proprietary to Oyen Digital's product line; the card can be used with other brands of external drives and devices Provides more bus power at the connector, max. 600mA combined for two ports  excellent for bus powered drives! Built-in DC jack for receiving extra power supply (DC to USB power y-cable included)