[UxmlAttribute(obsoleteNames = new string[] { "itemHeight", "item-height" })]public float fixedItemHeight { get; set; }

This property must be set when using the _virtualizationMethod is set to , for the collection view to function. If set when _virtualizationMethod is , it serves as the default height to help calculate the number of items necessary and the scrollable area, before items are laid out. It should be set to the minimum expected height of an item.