What size cover is used for the third grade math book in primary school, B5 or A4?

Some textbooks are different in different places.

Choose the right book cover according to the size of the textbook?

A5: length (from top to bottom)18.9cm * width (from left to right)13.6cm (weight: 90g/bag)

32K: length (from top to bottom) 2 1.2CM * width (from left to right) 15.6CM (weight 120g)

18K: length (from top to bottom) 24.5CM * width (from left to right) 17.6CM (weight: 155g/ bag)

16K: length (from top to bottom) 26.3CM * width (from left to right) 19.5CM (weight: 180g)

A4: length (from top to bottom) 30.2CM * width (from left to right) 22. 1 (weight 235g/ bag)