Will VITTSJÖ Shelf unit, black-brown/glass, 39 3/8x68 7/8 " fit in a Citroen C5 Aircross 2021?

The C5 Aircross gives you a wide, square loading mouth: 41″ across and 30¾″ tall, with a floor that is actually wider than the opening at 41¾″ between the arches. Seats up you get 38¼″ of length; folding them stretches that to 67¾″, a gain of 29½″. The catch is the sill, which sits 29⅛″ off the ground, though the floor drops only 1⅝″ behind it, so boxes slide in level rather than falling in. Wide flat packs do well here; very long ones run out of floor before they run out of mouth. Lift heavy boxes to sill height first, rest them, then push.

VITTSJÖ ships as one long, flat carton, 79¼″ × 15¼″ × 3½″ and 60 lb 12 oz. The length is the awkward part: a rigid flat-pack just under 80 inches that will not bend around a tight boot mouth, and there is glass inside, so the box does not forgive a hard knock. A car that takes it easily is an estate, an SUV, or a hatchback with the rear seats folded flat. In anything smaller, load it diagonally from a folded seat back toward the boot, longest edge leading, and rest it on a blanket. Keep it printed side up so the glass shelves stay flat, and slide it in rather than drop it.