Like most people Birkenstocks have helped you too! Most people who wear Birkenstock sandals and get relief will also use the Birkenstock Arch Support for shoes (it's the cork support that runs from the heel to the metatarsals - the one we talk about on our website). If you use it in your closed shoes and hiking boots and wear your Birkenstocks the other times your feet will never go without the proper support.
The insole is a rigid cork that will fit in most shoes and boots. When looking for a dress shoe it's a good idea to have the insert with you and put it in shoes you're trying.....they do work in flats very well.
If you have any other questions please let me know.
Regards,
Tony Grady