Fiber laser (20W) handles: All bare metals (stainless steel, aluminum, brass, copper, gold, silver, titanium), plus plastics, ceramics, and stone.
Diode laser (20W) handles: Wood, acrylic (opaque), leather, glass, slate, paper, rubber, fabric, coated metals, and anodized aluminum.
Cannot engrave: Clear/transparent acrylic (use opaque), PVC (releases toxic fumes), or materials thicker than cutting capacity.