Below 10mtr in height  

Form “B-1”

10 Mtr and above but not exceeding 15mtr

Form “B-2”

Above 15mtr but less than 16mtr

Form “B-3”

16mtr and above but not exceeding 24mtr in height   

Form “B-4”

Above 24mtr and not exceeding 30mtr in height  

Form “B-5”

Above 30mtr

Form “B-6”