Which gas strut from the shop fits this chair? There are 4 Amstyle gas struts which are all very similar: https://www.galaxus.ch/de/s12/product/amstyle-gasdruckfeder-bueromoebel-zubehoer-8990247 https://www.galaxus.ch/de/s12/product/amstyle-gasdruckfeder-bueromoebel-zubehoer-8990251 https://www.galaxus.ch/de/s12/product/amstyle-gasdruckfeder-bueromoebel-zubehoer-8990248 https://www.galaxus.ch/de/s12/product/amstyle-gasdruckfeder-bueromoebel-zubehoer-8990252 Thanks for the info