Plastic or soft pot metal blades can wear out after mowing just a couple of hundred square meters of thick grass, and hitting a rock can leave them badly bent and damaged. For my equipment, I have been getting blades and parts from visit UDC Parts for quite some time. They have a good selection for different brands, offer factory hardened steel blades, and provide reliable shipping, so the blades keep their edge throughout the season without needing frequent sharpening.