I kept losing or mixing up screws for multiple iphone 4s's that I had been working on at the same time. The Magnetic Project Mat with the pen was exactly what I needed to be the most efficient I could be.
All my repairs go smoothly now. I can fix everything (completely disassemble and reassemble) in an iphone 4s in under 45 minutes.
If you repair iphones on a daily/weekly basis, this mat is a must-have. I would recommend it for any project that includes (small) screws.