I successfully used this to resize the band on a Casio, and it was definitely easier than the makeshift blunt embroidery needle and meat mallet setup I'd been using before.  It was worth it to be able to resize by myself and test different configurations.  It also has two grooves to hold the band in case you want to do it the hammer and screwdriver way.  Operation is pretty self-explanatory if you understand how metal watch bands are held together. However, think of this as a disposable, not an investment.  You may in fact need those extra pins at some point, as they warp easily on more stubborn links, and you should be aware that the item is made of cheap, poorly-finished plastic. The depth adjuster setup is particularly atrocious.  For the price, it's OK as long as it's cheaper than going to a shop, but when you add the shipping cost, I do think that this item could probably have been sold for less.

Tips:  do not screw the pusher pins in too hard, as it can be hard to change them out, and make sure you check the size of the pusher pins; mine all appeared to be the same diameter, but others mentioned them being different.  Keep a finger on the watch band to keep it from slipping.  Tool will not fully push out pins, so have pliers (preferably coated to minimize chance of deforming watch pin) at hand to pull out pushed pins.  When putting pins back in, push or knock the pin almost all the way into the link before using pusher.