ME 030, ME 040, ME050, ME060 headers with vertical and horizontal plug-in direction are available with 2 to 22 positions. The header coding section is simply inserted in the corresponding slot. DECA ME headers have open-ended or with panels. The open-end version can be mounted in rows according to the pitch. There is no danger of lateral mismating in the versions with side panels. DECA ME headers can have treaded flange for vibration-resistant connection with the plugs with screw flange. ME 110, ME 130, ME13R, ME150,ME210, ME230, ME23L, ME23R,ME250 with double level headers (pitch 5 or 5.08 mm) in horizontal design. The prime advantage of a double-level ME series headers is the relative saving of printed circuit board sufface space. Extended constructions with more position can be created by mounting headers with flange or closed side panels to the right and to the left of the standard housing. ME 120, ME 140, ME 14L, ME160, ME220, ME240, ME24L, ME260 with double level headers (pitch 5 or 5.08 mm) in vertical design. As a result of modular ”building block” system of 2 and 3-position double level blocks, any number of positions from 2 to 24, can be obtained by simple interlocking, with or without flange. Extended constructions with more positions can be created by mounting headers with flange or closed side panels to the right and to the left of the standard housing.