Not to mention bloody expensive. I have no doubt it works really well for some women, but I'm not one of them. This is now cycle 5, it got my peak right first cycle, was a day late the second cycle and has failed to identify a peak since. It gave me 20 days of high readings last cycle, and this time I have a positive opk this morning and it's still giving me a low reading. It's going on eBay unless someone on here wants it!