Super-tough, water-repellent, reinforced 1/8" thick poly-coated fiberboard walls make these tubes ideal for safe storage or mailing of blueprints, drawings, documents, etc. Tubes are cover-wrapped with flat black finish. Nickel-plated metal screw caps, sealed metal bottoms. 3 1/8" inside diameter. Packaged 12/box. Can be purchased individually or by the box of 12.