Hi. You can make so: function OnReconfigure(sender, store, colModel) { sender.headerCt.forceFit=true; } or, for specified columns: function OnReconfigure(sender, store, colModel) { if (!sender.columnManager) { sender.columns[0].flex=1; } else { sender.columnManager.columns[0].flex=1; } } in unidbgrid.ClientEvents.ExtEvents