First, let me say that if you need the accuracy your life depends on, this product probably isn't for you. However, if everything is fine within one or thousandths of an inch, then go for it! It worked right out of the box and came with a spare battery and screw. The magnets worked great on my planing table, it was very stable yet easy to move around while I adjusted the blades. When I move the product abruptly/quickly it seems to go 1 or 2 thousandths from zero (I'll bet my cast iron planing table is perfectly flat) so I've often zeroed it between measurements, but in fact it wasn't like that. That's the big problem - super easy to make. The jointer cuts perfectly after adjusting the knives - very satisfied.