Keepsmiling, we can order the curved FRER on Amazon but they're quite expensive, although they seem to go up and down in price. They're actually rubbish imo because their threshold is so low that they have been giving some women false positive results. Their threshold is 6.5mIU, and we can have up to a level of 5 in us, so since it's possible for their threshold to vary a little per test, this is why (I'm assuming at least) so many have had false results. They're known for this unfortunately.
LuvallmyH, they're fabulous lines! I wouldn't worry about the FRER. Sometimes they take a while to become darker than the control line, I think I was about 6 weeks with DS2 when mine was darker than the control. But with DD it was darker right away. Different levels of hormones coupled with the tests varying in their own threshold and dye strength, makes them quite unreliable at times but those IC lines are absolutely amazing. And yes, the not having to bother holding and dehydrating yourself to the point of almost becoming a Pringle, and for once actually being able to pee in the toilet ... all good things lol