Direct3D 10.1 introduces "feature levels" 10_0 and 10_1, which allow use of only the hardware features defined in the specified version of Direct3D API. Direct3D 11 adds level 11_0 and "10 Level 9" - a subset of the Direct3D 10 API designed to run on Direct3D 9 hardware, which has three feature levels (9_1, 9_2 and 9_3) grouped by common capabilities of "low", "med" and "high-end" video cards; the runtime directly uses Direct3D 9 DDI provided in all WDDM drivers. Feature level 11_1 has been introduced with Direct3D 11.1.