The Merck Serono New Fertility Pen 1.0/1.1 pen injectors are used during the hormone treatment of patients trying to have children. With the help of a dosing scale, the amount of medication can be selected. The dose window displays only a single dose at any moment in time, making it immediately discernible as to whether the complete dose has been delivered, and thereby reducing the risk of dosing errors. The pens can be distinguished thanks to their colours and labels.