The Proton M's improvements included lower stage modifications to reduce structural mass, increase thrust, and fully use propellants. Generally a Briz-M ( meaning "Breeze") storable propellant upper stage is used instead of the Blok D or Blok DM stage, removing the need for multiple fuel supplies and oxygen top-off due to boiling; the Proton-M also flew with a Blok-DM upper stage. Efforts were also made to reduce dependency on foreign (usually Ukrainian) component suppliers. With the Briz-M upper stage, the payload fairing diameter is 4.1 m (13.45 ft).