2500 / D2500 Four-Wall Box Headers 3M Connectors 2500 / D2500 Four-Wall Box Headers feature a low-profile, space-saving design that measures 0.100' x 0.100'. These connectors are available in surface-mount and through-hole versions. The through-hole version is suitable for reflow soldering using 'paste-in-hole' techniques. Exposed solder tails (on right-angle versions) offer ease of cleaning and reduced repair costs. 3M Connectors 2500 / D2500 Four-Wall Box Headers provide a center-slot polarization to reduce insertion time and prevent incorrect insertions.