Lining a chimney flue is strongly recommended for all new multi-fuel and wood burning stove installations, especially in the older properties. In addition, current regulations state that all chimney flues of 12 metres or more in height must be lined before any solid fuel appliances are installed.
Grades 316 and 904 chimney lining
The difference is purely one of quality. 904 grade is a higher grade stainless steel than 316 grade and is less likely to rust from the outside or corrode from the inside. 904 and 316 are terms used within the stainless steel industry.
Choose 904 if you want belt and braces quality or you are going to burn smokeless fuel or coal. Choose 316 if you are on a budget and you only intend to burn seasoned (dry) wood.