What kind of brackets are used?

I have measured again and can say that you would even have 308mm to the clamp. The Bostitch has a grid of 2mm on the lower side where you can adjust the stop. In addition, the steps A6 to A2 are printed on it. On the opposite side, inch sizes are also marked with Legal,Letter. I have already used Leitz P5 staples for up to 60 pages. However, I would not recommend larger staples as the device is actually only designed for up to 40 sheets and the staples already partially break off in the sheet at 60 pages. I ordered the staples from Buch.ch.

The maximum format is A2. The extension is stepless and there are markings for the different formats.