the Convention on the Harmonized Commodity Description and Coding System, have agreed to base their national tariff schedules on the HS nomenclature and Legal Notes. Parties are permitted to subdivide the HS nomenclature beyond 6-digits and add their own Legal Notes according to their own tariff and statistical requirements. Parties often set their customs duties at the 8-digit "tariff code" level. Statistical suffixes are often added to the 8-digit tariff code for a total of 10 digits. If the number of digits are more than 8, additional digits are called as the national subheading. HS Chapter 77 is reserved for common use by the parties internationally. Chapters 98 and 99 are reserved for national use. Chapter 98 comprises special classification provisions, and chapter 99 contains temporary modifications pursuant to a parties' national directive or legislation. Since its creation, the HS has undergone several revisions - ostensibly, to either eliminate headings and subheadings describing commodities that are no longer traded, or to create headings and subheadings that address technological advancements and environmental concerns. The current version of the HS became effective on 1 January 2017. Classification The process of assigning HS codes is known as "HS Classification". All products can be classified in the HS by using the General Rules for the Interpretation of the Harmonized System ("GRI"). HS codes can be determined by a variety of factors including a product's composition, its form and its function. An example of a product classified according to its form would be whole potatoes. The classification will also change depending on whether the potatoes are fresh or frozen. Fresh potatoes are classified in position 0701.90, under the Header Potatoes, fresh or chilled, Sub header Other, while frozen potatoes are classified in position 0710.10 under the Header Vegetables (uncooked or cooked by steaming or boiling in water), frozen, Subheader Potatoes. The Harmonized System has six general interpretative rules that must be analyzed in strict order. An example of a product classified according its material composition is a picture frame. Picture frames made of wood are classified under subheading 4414.00, which provides for Wooden frames for paintings, photographs, mirrors or similar objects. Picture frames made of plastic are classified under subheading 3924.90, which provides for Tableware, kitchenware, other household articles and hygienic or toilet articles, of plastics. Other. Picture frames made of glass are classified under subheading 7020.00, which provides for Other articles of glass. And