The mains power cable to Islay and Jura has broken and we rely on generators into the forseeable future, with all the unexpected fluctuations and breaks in supply that are inevitable. I wanted something that might avoid needless corruption or loss of work - as far as I can see, this unit does the trick. The scanty instructions were enough for even my limited skills (although the Product Number refers to the outside of the sleeve of the software, not to the Product itself!) and the unit seems to close the PC in a measured way. We get up to three or four power cuts on a bad day, sometimes none - I am quite happy with my purchase but note that I am using it on one stand-alone PC.