Pebbled-grain PU (faux) leather with a knot-style loop fastening — no pin or notch holes, so length is set entirely by how you tie it. Wipe clean with a damp cloth and mild soap; never machine wash or soak, and keep away from direct heat which can crack the coating. Because the whole strap flexes and re-knots with every wear, it's worth avoiding sharp creasing at the same fold point repeatedly, which can eventually weaken the coating along that line.