I found mine great until I broke it hehe.

As I have said before, its not something to ACTUALLY pinpoint ovulation but a tool to work out your fertile days.
I found you had to have the right saliva amout, correct drying time and not to use it within an hour of drinking or eating.

For someone like me who hardly gets noticeable CM or good OPK results, this worked for me.

The first month I used it I got a BFP two weeks later.!!