Alvin BTR4 Black Knight Storage Tube, 4 1/4 inches Made of durable black plastic, tube is water-resistant. Ideal for storage, protection, and transport of documents, artwork, prints, posters, and more. Expands from 30 inches to 45 inches in 14 locking 1 inches increments with a 4 1/4 inches inside diameter. Includes removable, adjustable shoulder strap. Size: 4 1/4"