The Rock Exotica Brake Tube is made from two pieces of aluminum tubing welded together. A rod safety ensures that the rope stays on the spool. The closure (in red) is threaded on the lower side (as shown). There are no threads on the upper guide piece. Since this piece is not loaded, there is no need for the strength that threads would provide, and threads that aren't there can't be exposed to damage. The maximum opening is about 17 mm, large enough for any reasonable rope. The eye loop is welded stainless steel, so it cannot come out of the tube.
The Brake Tube can be rigged as a horizontal spool. In this arrangement it gives excellent control and induces little to no rope twisting. It can also be rigged as a vertical spool, but this will twist the rope more.
Petzl bought the rights to most of Rock Exotica's products, and now manufactures this as the D12 Tuba.
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