The GF Heavy Duty Series is a classic collection of larger, and heavier knives for general preparation. This range, being more durable for heavy use, is favored by many professional chefs. In Japan the term for the heavier chef knife would be yo-deba. Many Japanese Cutlers make a knife in two different thicknesses with the same basic shape and length, and it is very difficult to see the distinction in a picture. So, when you see the term yo-deba, or heavy chef knife, it means that the blade is significantly thicker and heavier than the traditional chef knife. In this case the Global G-Series is a traditional, thin, light Japanese knife, and the GF series is roughly double the blade thickness and considerably heavier.