I started by cutting a medium and then a heavy 4-5 oz leather. The blade worked very well. I cut out several key cases with this. I was quite pleased with the accuracy and it was accomplished in only 4 passes. As you will find, leather does make a mess on the Cricut mat, and will need to be cleaned. You may want to look on the internet for hints on dying leather colors. I found that it hardened the leather, and then found better ways to dye the leather, but this is a review of the Knife Blade which I am anxious to find more projects that I want to accomplish with this blade.