i get this every day just now, either the customer is too slim in the calf or too chunky. There are alot of elasticine boots in all styles that are great as they cling to the leg and stretch to fit any size, trouble is people usually prefer a leather boot, it's the same in life, we always wanmt what we can't have. people with this sort of issue are better going for ankle boots or calf length boots that fit snuggly around the back of the calf. It will look better especially with slim calves, as tall boots end up looking like wellies.