I agree Tingly, I've got more info from here too.. and I've gone to my GP armed with far more information - and fortunately she's happy to listen and doesn't mind if I have got help from the internet (my previous GP used to go mad if you mentioned you'd looked stuff up!) So far the estring seems OK.. still can't feel it, don't know it's there and the very minor tummy ache has gone. The whole ring has 2mg of estradiol which spreads over 3 months which is more than the vagifem. It says it releases 7.5 micrograms over 24 hours. I guess for those noticing that 2 vagifem a week isn't working well, the estring might be good but the extra is worrying me to be honest. 2 x weekly vagifem is still only 1.14 mg a year whereas the estring will be 8 mg.