Custom Listing: Single Piece - 18x24Custom Listing: Single Piece 18x24 All posters are printed on high quality 255 gsm 68 lb professional paper with high end professional grade equipment. I ship smaller size posters (5x7 and 8x10) flat, supported with 2 cardboards in a bubble envelope and larger size posters rolled in mailing tubes. Rolled posters can easily be rolled towards the opposite size to flatten. I use professional quality paper that is not effected by rolling. It will flatten