Inner diameter is a standard 1 1/4Inch (32mm) and 1 3/8Inch (35mm) size for most vacuum brands There is a suction adjustment button on the brush.You can adjust the suction as required.It is a high quality brush with smooth rolling wheels,PP hair If you pull these two "arrows buttons" out ,the dust holder head will be disassembled.This new design will help you to clean the brush clearly and quickly The brush will take good care of house floor and furniture Please check the instruction manual paper in the package.Designed and manufactured by EZ SPARES.Good quality and long service life.If you have any questions, please feel free to contact us.