The SirenHorn is a unique horn that makes a siren noise that Japanese police cars make. In order to obtain it, a purchase can be made from Cheese upon agreeing to buy his mystery part for 400(units) which will provide the Police Lights. Technically, one can accept his offer for 200(units), BUT by accepting it for that amount, one would miss the opportunity to obtain the SirenHorn. Thus, it is important to accept the initial offer of 400(units).