CFexpress Type A and CFexpress Type B memory cards are both PCIe-based, although their physical dimensions and transfer speeds differ. CFexpress Type B measures 29.8mm(Width)*38.5mm(Height)*3.8mm(Thickness), whereas CFexpress Type A measures 20mm(Width) x 28mm(Height) x 2.8mm(Thickness). Type A cards can theoretically transfer 1,000MB/s, while Type B cards can theoretically transfer 2,000MB/s.