I prefer to have my spool holder off to the left away from the printer's wires, but I found that when you put a full 1kg spool on it, the control box will have a tendency to tip over until some of the filament has been used. You can counteract that by placing something heavy (like another spool) on top of the box, but I decided to design this stabilizer to solve the problem. Just slide it onto the rear of the control box, avoiding the rubber feet and screws, etc. This fits my control box tightly, but of course it's difficult to know how different settings and filaments will be. This will also work on the CR-10 S4, and presumably the S5, but I don't have the S5 to check.