Disclosed is a single-use bioreactor bag design providing substantially equivalent maximum shear rate at the impeller tip and average or bulk shear rate over a range of power per unit working volume and rpm needed for bioculture processing. The uniformity in shear profile of the bag design providing a unique advantage when used as a scale-down or scale-up platform. Also disclosed is a linearly scalable, single-use, bioreactor system for use in carrying out a scalable biomanufacturing process, the system comprising two single-use bioreactor bags of different volumes, wherein the ratio H/D of the height of the working volume H to the diameter D of the tank, or of the bag is equal to about 1.5, and the bulk shear in each of the bags is substantially constant. The disclosed small scale system models larger scale systems from both a shear/scalability/performance basis and also from a validation and regulatory basis. In summary, the 10L bioreactor system disclosed provides for “linear scalability” by using the same or substantially simulating the same vessel geometry, gas sparging system, impeller shape and type, polymer composition of the flexible bag/components, process control system, and shear rates as larger 50-5000 L systems.