Materials From Our Workshop: Horween Leather & Fil Au Chinois Thread When it comes to choosing leather at Minimum Squared, you could say we’re hard to please. We’re committed to working with only the very best, most sustainable materials. That’s why we choose Horween leather to make several of our wallets. Horween leather might be world-famous, but it’s also one of our favourites, along with a couple of world-class materials we never get tired of using. Here’s why.