Black Smoke Apparel uses Full Grain Leather for all of Career Warranty Leather tools. What is Full Grain Leather??? The strongest and most durable part of the animal is right below the hair. The grain pattern in this part of the hide is very tight, and the leather made from here is called "full-grain" leather. Full-grain leather is the strongest and most durable leather. Additionally, since the grain is so tight, it resists moisture very well. Over time, full-grain leather will look nicer and develop a patina from being handled.