My hubby, who worked on an NRCS snow survey team, has tried a bunch of products (he's fairly obsessed with his boot leather), and right now he uses Nikwax, which can be used for a variety of gear. http://www.nikwax.co.uk/en-us/index.php He says that conditioners/waterproofers with animal fats in them will degrade leather over time. Needless to say, I just pass him my boots & let him do his thing