Flex frames are used for the opening of glasses cases or coin purses.
To instal all you do is slide the open flex frame through each sides of your pouch according to your patterns instructions and slide in the pin to join it back together and then close the ends with a pair of pliers to secure the pin in place.
We stock 10cm and 12cm
Cost $2 Each
If you search google Flex Frame patterns there are a few free patterns and tutorials for these.