Several of the popular RISC and CISC microprocessors are using the same logial and electrical layer for their high speed local bus. These same RISC and CISC processors are being incorporated onto single slot VME boards, Multibus boards, desktop computers and other types of computer system. There is a large market need for modular I/O and modular local function expansion via low profile mezzanine cards. This proposed standard will be the parent document for a series of mezzanine cards, plus will define the base line mechanics for these mezzanine cards that can be used on VME, Multibus, desktop computers and other computer based applications with a similar need. The mechanical definition will be based on IEEE 1301.4 and the other hard metric mechanical standards. A suggested set of environmental standards will be referenced for the environmental layer.