Bakeware, Tableware, Drinkware and Cookware Design Sumu Series Cutlery by Mitsunori Yamase SUMU is one of cutlery series made of zirconia. They do not interfere with the flavours of dishes as absolutely no metallic ions are released. Consequently, they never become the cause of metallic allergies. You can focus on your sense of taste as the thin, silky finish of the zirconia tip makes it easy to take hold of the food with exceptionally smooth feeling in and out of the mouth. The matte zirconia cutleries softly reflecting atmospheric lighting shall bring serenity to the dining scene.