Each box set includes 20 pairs of Rescue Flats: 5 Small, 10 Medium and 5 large. We have been a part of over 14,000 weddings and have found that this is typically the size range that you will need. Rescue Flats have a flexible fit and each size can comfortably fit a wide range of sizes. For example, if you wear a US women’s size 8, you can comfortably fit in both Rescue Flats size small and medium. If you wear a 9.5, you can comfortably fit in both medium and large.