A flexible package is designed to contain a product, for instance a spice or a cosmetic product, and the flexible package is formed of at least two layers of flexible material joined together to create a closed package (volume). A dosage device is arranged on an inner face of the closed package, and the dosage device includes an elastic dosage membrane having a number of incisions over at least a part of its width and length, and includes an opening device configured to stretch the elastic dosage membrane.