An office chair or office chair element, in particular a backrest or seat, including a flat covering element, in particular a fabric, cushioning or webbing element, which is secured to support elements, for example to the arms of a support frame, and tensioned between the same, - wherein the covering element is provided with at least one welt strip on its outside edge, - wherein the welt strip, in the fitted state, is placed in an accommodating groove realized on the support element, - wherein the accommodating groove has two oppositely situated contact faces (5, 6) for the welt strip and one of the contact faces is provided with a projection that projects into the accommodating groove and extends in the longitudinal direction of the groove, - wherein the welt strip is insertable into the accommodating groove by being pressed into the accommodating groove, thereby resiliently deforming the projection and/or the welt strip, - wherein the welt strip, in the fitted state, is placed in the accommodating groove in a positive locking and/or force-locking manner abutting against the contact faces (5, 6), thereby being prevented from escaping from the accommodating groove by the projection, - wherein the welt strip has two oppositely situated side faces (12, 13) and two oppositely situated end faces (11, 14), wherein the welt strip is insertable into the accommodating groove by being pressed with one of its end faces to the fore into the accommodating groove, and wherein the welt strip, in the fitted state, abuts against the contact faces (5, 6) of the accommodating groove with its side faces (12, 13), and - wherein the welt strip has a clamping strip, which extends in the longitudinal direction of the strip and, in the fitted state, abuts against the projection. - wherein the covering element is provided with at least one welt strip on its outside edge, - wherein the welt strip, in the fitted state, is placed in an accommodating groove realized on the support element, - wherein the accommodating groove has two oppositely situated contact faces (5, 6) for the welt strip and one of the contact faces is provided with a projection that projects into the accommodating groove and extends in the longitudinal direction of the groove, - wherein the welt strip is insertable into the accommodating groove by being pressed into the accommodating groove, thereby resiliently deforming the projection and/or the welt strip, - wherein the welt strip, in the fitted state, is placed in the accommodating groove in a positive locking and/or force-locking manner abutting against the contact faces (5, 6), thereby being prevented from escaping from the accommodating groove by the projection, - wherein the welt strip has two oppositely situated side faces (12, 13) and two oppositely situated end faces (11, 14), wherein the welt strip is insertable into the accommodating groove by being pressed with one of its end faces to the fore into the accommodating groove, and wherein the welt strip, in the fitted state, abuts against the contact faces (5, 6) of the accommodating groove with its side faces (12, 13), and - wherein the welt strip has a clamping strip, which extends in the longitudinal direction of the strip and, in the fitted state, abuts against the projection.