The Sonotube Builder's Tube 12 in. x 4 ft. Concrete Form Tube is an extra-strong fiber form for pouring round concrete footings and posts for decks, fences, mailboxes and play structures. It is built from multiple layers of high-quality fiber, spiral wound and laminated with a heavy-duty adhesive to withstand the pressure of wet concrete. Designed for below-grade use, it can be poured up to 3 ft. above the ground line and holds approximately 3.14 cu. ft. of concrete.

• No bracing needed unless the form extends more than 2 ft. above ground line
• Designed to be left in place, or cut away vertically after a 24-hour cure
• Make sure the tube is dry before filling, and do not use mechanical vibration
• Set up all tubes in advance to pour the whole job at once