My wife bought me that exact set as a surprise for my birthday 2 weeks back.
They seem pretty well made given the price and the storage bag with separate compartments for each level will come in very handy. I haven't had chance to use them in anger yet but have tested them and they seem as accurate as I'd ever need. Place them on a relatively level surface (I used my dining table) and check where the bubble sits. Spin them around end to end and if the bubble is in exactly the same place you know they are accurate. Mine were all as perfect as my eyes could make out.
Would definitely recommend.