I recently had a letter from a women who had a problem with being unable to find the correct high heel shoes (or ballet flats) that would properly fit her narrow foot, especially at the heel. She had also been unsuccessful in finding the correct shoe inserts to place into her shoes to make them more wearable and comfortable. This is a common problem because many commonly available shoes come only in medium width. There are also issues with some shoe manufacturers who use the same shoe last for womens' and mens' shoes, adjusting only for size and not overall dimensions. The problems with many shoe inserts is that they are made from silicon gel, which is very cheap to manufacture by the process of molding, however it is slippery underfoot especially when it gets damp, does not have much shock absorption capacity, cannot be firmly attached to the inside of a shoe therefore it falls out of a shoe easily, and is often too thick and bulky so it pushes the foot out of the heel area when used there as gel strips or even out of the shoe itself if it is a 3/4 gel insole that goes under the heel of the shoe and has a raised area under the arch.
This is my letter to the women with fitting issues of her narrow feet (my real letter but not her real name) :
Dear Mariah, Thank you for your letter. I think my inserts for high heels would help you with the problem of your heels slipping, presumably sideways and falling off or slipping forwards because they are not held in snugly at the heel end of the high heel shoe.