An apparatus for removing impurities from staple fibers for ringless spinning in spinning units, comprising a hollow body, a fiber opening roller rotatable in said hollow body, said hollow body having a supply passage through which unopened fibers are supplied to said opening roller, and a spinning chamber, said hollow body having an opened fiber discharge passage through which opened fibers pass from said opening roller to said spinning chamber, and said hollow body having an impurities discharge passage between said fiber supply passage and said opened fiber discharge passage for discharge therethrough of impurities from fiber being opened by said opening roller, said impurities discharge passage extending through the hollow body generally tangentially to the periphery of the fiber opening roller, said hollow body including a wall extending substantially tangentially to the periphery of the fiber opening roller, located so that the adjacent portion of the fiber opening roller periphery moves towards said wall and constituting a wall of the impurities discharge passage.