A method and a device for opening and dosing fiber feeds the fiber material via a feeding shaft of an opening device. The fiber material is processed in a first opening step of a dosing opener and is fed without an interconnecting pneumatic means to the feeding shaft of a second opening step. A large-volume feeding shaft has been placed before the first opening device from which the fiber material is delivered to a feeding shaft with a considerably smaller volume that delivers the fiber material to a second opening device. Both opening devices and their associated feeding shafts are placed on top of one other.