Building panels provided with a locking system for vertical locking of a first and a second building panel by a vertical displacement of the panels (1,1') relative each other, the building panels comprising: a sidewardly open tongue groove provided at an edge of the first building panel, and a strip protruding below the tongue groove and outwardly beyond an upper part of the edge of said first building panel; a displaceable tongue provided in a sidewardly open displacement groove at an edge of the second building panel, the displaceable tongue comprising a main body extending along the edge of the second panel and a tongue locking surface located at an upper and outer part of the tongue, the tongue locking surface being configured to cooperate for vertical locking with a groove locking surface of the tongue groove, wherein the displaceable tongue comprises an inner part spaced inwardly from an upper part of the edge of said second panel, and wherein the strip comprises a locking element configured to cooperate with a downwardly open locking groove, formed on the second panel, for locking of the first and the second building panel (1,1') in a horizontal direction, characterised in that the inner part comprises a tongue pressing surface configured to cooperate with a strip pressing surface on the strip, such that the displaceable tongue is displaced into the tongue groove when the tongue pressing surface and the strip pressing surface (32,33) are displaced vertically against each other to obtain a locking of the first and the second building panel (1,1') in a vertical direction, that said displaceable tongue is asymmetric and comprises a protrusion extending from the main body and the second panel comprises a cavity for housing the protrusion, that the tongue pressing surface is provided on the protrusion and the strip pressing surface is provided on the locking element, that the strip pressing surface is provided at an inclined surface of the locking element directed towards the edge of the first building panel, and that the displaceable tongue is an injection-moulded tongue. a sidewardly open tongue groove provided at an edge of the first building panel, and a strip protruding below the tongue groove and outwardly beyond an upper part of the edge of said first building panel; a displaceable tongue provided in a sidewardly open displacement groove at an edge of the second building panel, the displaceable tongue comprising a main body extending along the edge of the second panel and a tongue locking surface located at an upper and outer part of the tongue, the tongue locking surface being configured to cooperate for vertical locking with a groove locking surface of the tongue groove, wherein the displaceable tongue comprises an inner part spaced inwardly from an upper part of the edge of said second panel, and wherein the strip comprises a locking element configured to cooperate with a downwardly open locking groove, formed on the second panel, for locking of the first and the second building panel (1,1') in a horizontal direction, characterised in that the inner part comprises a tongue pressing surface configured to cooperate with a strip pressing surface on the strip, such that the displaceable tongue is displaced into the tongue groove when the tongue pressing surface and the strip pressing surface (32,33) are displaced vertically against each other to obtain a locking of the first and the second building panel (1,1') in a vertical direction, that said displaceable tongue is asymmetric and comprises a protrusion extending from the main body and the second panel comprises a cavity for housing the protrusion, that the tongue pressing surface is provided on the protrusion and the strip pressing surface is provided on the locking element, that the strip pressing surface is provided at an inclined surface of the locking element directed towards the edge of the first building panel, and that the displaceable tongue is an injection-moulded tongue.