In most board-to-board applications, designs require that the boards are pluggable. This allows for easy replacement in the event of board failure, more streamlined manufacturing for applications with multiple add-on board options and ease of upgradeability or accommodation of future design changes.
In these type of applications, the same male headers in single and dual-row configurations are mated with female sockets. Mating different combinations of headers and sockets will create different between-board spaces. The header tail diameters need to be within the mating socket’s diameter acceptance range.