voltage regulator

[Naruto128]

http://www.ebay.com/itm/DC-DC-Adjustable-Step-up-Power-Converter-Module-XL6009-4A-maximum-current-/171192014452?pt=LH_DefaultDomain_0&hash=item27dbd6d674

I use this?

but it behaves like a voltage regulator?
ie, if a 9v battery I connect the DC / DC converter., and battery
begins to discharge up to 6 volts, the output of the DC / DC converter, maintains
5v?