One of the largest categories of connector types, printed circuit board (PCB) connectors are designed to be mounted or processed to a printed circuit board. There are two primary categories of PCB connectors; board-to-board and wire-to-board. Both types improve manufacturability by allowing equipment to be manufactured in small sub-systems that later are plugged together. The use of these sub-systems also allows for design flexibility (meeting of customer specific requirements) and easier repair and upgrade of a system in the future. The most common PCB connector types include one-piece card edge; PCI Express, Micro TCA, and VRM connectors and two-piece board-to-board; FFC/FPC, stacking connectors, wire-to-board, DIN41612, PCMCIA, M55302, memory/adapter card sockets, backplane and mezzanine connectors, as well as square/round post headers and receptacles.