Hey, I know you got your tests back but just to answer the question, they have a sensitivity of 25 mIU's but they have been known to detect down to 7. I'm glad you said yours have gotten darker over the day because mine have to. Usually evaps fade. Mine is as wide as the control line to and all one normal blue color, not weird funky lines. I'm not supposed to start until Thursday so hopefully mine get darker. I'm so happy that your quant was + and that your tests are getting darker!!!!!!! congrats!!!!!!!!! =)
Approximately 25 miu.
Here is a very informative website regarding HPT's and OPK's
http://www.peeonastick.com/hpts.html