Transcend's JetDrive Lite expansion , around a third of the size of an SD cards, these MLC flash (a type of NAND memory) cards can boost a 13- or 15-inch MacBook Pro's storage capacity by slotting into its SD card slot. Unlike regular SD cards that stick out of the side, Transcend's offerings can be fully inserted to the point where the card is practically indistinguishable to the machine's edge.