I have bought a couple of watches online lately and wanted to be able to adjust them myself instead of paying $10 each time.  The kit has everything you need and the instructions on the website provided are easy to follow.  Took me about 5 minutes to resize my first watch and it was super simple.

This kit was definitely something I never realized I needed, but now that I have one I'm glad I will never need to pay to have a watch resized again.