Pinit 3 x 3 x 18" Square Mailing Tube with built-in end caps. Made from white-one-side 200-pound-test corrugated. SKU: MTSQ318 (0)No Reviews yet Add to Shopping Cart Details Square Mailing Tube with built-in end caps Inside dimensions: 3 x 3 x18" Made from 200-pound-test white-one-side corrugated cardboard. Ship and store... Details Back DetailsSquare Mailing Tube with built-in end caps Inside dimensions: 3 x 3 x18" Made from 200-pound-test white-one-side corrugated cardboard.Ship and store flat. These one-piece mailers just fold together. Square construction makes packing and shipping easy! Reviews 0 Back Ratings & ReviewsNo reviews availableBe the first to Write a Review