The number of hanks of 300 yards in a pound is called linen count (lea). It is specially used to express the fineness of flax (linen) yarn. The yarn becomes finer when the count increases in this system.
If the weight of yarn is w grams, and the length of yarn is L meters then the lea count of yarn is obtained as follows.
Lea can generally range from 10 to 120
20 is very heavy and thick
120 is superfine and basically see through
60 is about the limit that pants can be made from before it’s to fine for pants
Shirts can go up to 120
Linen is machine washable, best at 40 to 60 degrees Celsius
Low to medium heat dry