US Patent 7547229 Stacked electrical card connector having stand off

An stacked electrical card connector comprises: a first connector comprising an insulative housing and a first shell covering the insulative housing, said first shell comprising a plurality of retention pieces extending outwardly; a second connector stacking with the first connector, comprising a bottom plate with a protrusion extending outwardly; at least one stand off for combining the first connector and the second connector together, comprising an engagement portion with a group of openings, and one of the openings comprising an elastic piece therein, said retention pieces and protrusion retaining in corresponding openings of the stand off, and the elastic piece withstanding on one of the retention piece in the front-to-back direction.