The red herring prospectus is used to solicit expressions of interest in the issue. Once the registration statement becomes effective, a final prospectus that contains the final IPO price and issue size is disseminated. Expressions of interest are then converted to orders for the issue at the buyer’s option.
The minimum period between the time a registration statement is filed and its effective date is 20 days. Note that the SEC does not approve the securities but simply ensures that all relevant information is disclosed in the registration statement.