The holes also allow the use of quick cylinders fixings - Quick APD - belt.
The cylinder fixing are not included.
The travel can be used in configuration 2 or 4 cylinders of 2 or 3 liters.
It can be used with original APD harness or with classic harness with backplate.
It can be used with front or rear lungs.
Undoubtedly has the advantage compared to the original case to use for diving decidedly less weight, the possibility of simply mount different types of cylinders, the simplicity and robustness of the system.