If you happened to use the wrong or inferior product (silicon wax/polish, because you didn't know better) over the years on your quality leather shoes/boot this is the product to use (think of this cleaner like a master reset to save your leather shoes). Before you go about using it, I recommend doing it in a well-ventilated room, spare couple of hours, elbow strength, leather conditioner, a lot of cotton cloths and highly recommend a pair of shoe tree.
I also highly recommend the rest of Saphir's care product if you happen to be replacing whatever you had on the shelve from your local supermarket.
Buy once cry once. Happy cleaning.