Will KALLAX Shelf unit, white, 30 1/8x57 5/8 " fit in a Peugeot 5008 2021?

This trunk lives two lives. With all rows up the 5008 gives you a 13⅜″ shelf, groceries and not much more. Fold the seats and the floor runs 74″ deep, a +60⅝″ swing, behind an opening 44½″ wide × 31½″ tall. The floor stays 45¼″ across at its narrowest, wider than the mouth itself, so any box that clears the opening will sit flat inside. The liftover is 27⅛″ with a ⅜″ drop to the floor, close to flush, so you slide heavy boxes in instead of lowering them. Long flat packs are the easy case; tall cartons still have to duck under that 31½″ opening, so check height first on borderline boxes.

The KALLAX comes as a single flat carton, 59″ × 16″ × 6½″, and it carries real weight at 68 lb 5 oz for one box. It is a stiff, square-edged panel pack: not long enough to be unmanageable, but wide at 16″ and heavy enough that you will not want to hold it out at arm's length. A hatchback with the rear seats folded usually takes it, and an estate or SUV takes it without thinking. The weight is the thing to plan for. Keep it flat, slide it across the boot floor, and load it last.