Non-rectangular or rectangular interposers for space efficient, reliable to manufacture, high speed interconnections between two printed circuit boards, such as a motherboard and a mating board. One example provides space efficiency with a non-rectangular interposer, where the interposer may be at least approximately circular. Reliable manufacturing may be provided by the inclusion of one or more openings to accept one or more alignment features. In one example, a first opening is provided to accept a threaded boss, which may be used to fasten the two printed circuit boards and interposer together. In another example, a second opening may be provided to accept an alignment post, wherein the post aligns the interposer to the two printed circuit boards. Contacts may be provided on each side to mate with contacts on each of the two printed circuit boards.