Let us begin by understanding what is book building? It needs to be understood that book building is a process of price discovery. The issuer discloses a price band or floor price before opening of the issue of the securities offered. On the basis of the demands received at various price levels within the price band specified by the issuer, Book Running Lead Manager (BRLM) in close consultation with the issuer arrives at a price at which the security offered by the issuer, can be issued. You also need to understand what exactly a price band in a book built issue is. Book built issues do not have a fixed price but they set a price band and then the price is discovered through an iterative process. So, what is the price band? The price band is a range of price within which investors can bid. The spread between the floor and the cap of the price band shall not be more than 20%. The price band can be revised. If revised, the bidding period shall be extended for a further period of three days, subject to the total bidding period not exceeding ten days.