It’s quite thick, 2mm. There are specific leather needles which you absolutely need, probably a good idea to use thicker nylon thread instead of cotton, and the longest stitch length. Also I had to use this stepper foot, the teeth couldn’t grip the leather to move it otherwise. All in all it’s stretching the limits of what a household sewing machine can do, one of my machines just couldn’t do it at all, didn’t have the oomph