The Treeline Stackable A4 Desk Letter Tray Single Units feature durable, open-front moulded plastic filing structures. The ventilated bottom design enhances airflow to protect documents from moisture damage. These loose, individual units let users customize their vertical desk layout configurations precisely. The space-saving template is available in corporate Black, Standard Blue, vibrant Red, Green, Azure Blue, Lime Green, Hot Pink, and Electric Purple. (Note: Stacking risers and window indicator clips are sold separately for loose items).