The main feature of our Low Cut Liner Socks is INVISIBLE(not only make it be covered on your foot minimum,but also stay on your foot),hence the fabric must be highly elastic to cover your foot. If the size is not fit for you foot, it will slip off. So, we manufactured different sizes for different customers' needs from Oct,2016. If the size you purchased doesn't fit you, please contact with us for another size (It's FREE)!!! Also, we noted some customers advise us the fore-foot cushion is too thick, considered it will be make some tight shoes more tight with a cushion, we manufactured another style without cushion,please search "CAcB" for more choices. FBA Shipment is Available on the item marked as "Fulfilled by Amazon" and Regarding items marked as "Ships from and Sold by CAcB",FREE SHIPPING is available and needs lees than 15 days for shipping.