The Lone Wolf Leather Apple iWatch Strap in Horween's natural Chromexcel is made of two layers of leather hand stitched with brown thread. Chromexcel leather is a mix of two tanning methods resulting in a soft and full leather that patinas well with use. As it ages and the top dye wears the brown core of the leather will show. This is called "tea core". The leather is hot stuffed with oils and waxes giving it the characteristic chromexcel pull up. Chromexcel is used for both the outside and inside leather of the strap making it a robust 3.6 mm thick.