These tubes originally held powder charges for howitzers, but they make great storage tubes for anything you want to keep nice and dry. The inside is 6” across and 25” deep, exterior dimensions are 28.5”x9” across (sizes may vary slightly). They weigh approximately 15 pounds, these are very well made. The lid is held in place by three lugs that screw to very securely clamp it down, and sealed by a very think o-ring. These will hold most M4 style AR uppers and the lower if you remove the pistol grip and slide the stock off the buffer tube, ammo, brass, powder, etc. They are a great way to keep things nice, safe and dry. A customer of mine got some of these and set them in the foundation of his garage when he poured it to make an inexpensive in-foundation safe. There are hundreds of possible uses for these. A padlock can be placed in the slot where the lug on the cap engages to lock these up where the cap cannot be removed.