Preglued style (shown)
A simple construction in which commonly functions as the slip-on cover for a two piece combination of a tray & sleeve. Additionally, this style is used as the basic structure for many high-end multi-packaging systems. Such sleeve styles may feature either a locked-side seam or glued seam version.
For example, today many food companies use this style sleeve to advertise their product which slips over their oven/microwave friendly frozen or fresh packaged food tray.