A dispensing assembly includes a double cartridge having two storage containers with bags placed therein, a mixer that is connectable to the cartridge, and an opening device acting upon the bag. The opening device is arranged on the mixer housing and rotatable with respect to the cartridge and has a cutting member including two knife-edges that acts essentially perpendicular to the longitudinal axis of the bags within the cartridge. Due to the knife-edges being rotatable and arranged laterally with respect to the bags, the cutting member allows a clean and predetermined opening of the bags and a dispensing operation with minimum pressure losses and lost volumes.