You need a black base that doesn't look like you grabbed a piece of card from the bin liner. This is a proper deep, even black at 200gsm — no white showing through when you layer it, no streaks where the glue seeps in. At project size (510 x 640mm) you've got a full sheet to cut your shape out of, and the weight means it stands on its own for a while before you tack it down. Whether it's a border for a science fair poster or the backing for a 3D model, this is the black that looks intentional. Cut it, fold it, stick it up. Sorted