A fluid pump , comprising: a drive shaft having an axis of rotation , driven for rotation in at least one direction, the drive shaft having at least one planar first drive surface (30a or 30b) formed on a portion of the length of the drive shaft, at least one planar second drive surface (30d or 30c) formed on a portion of the length of the drive shaft, and when multiple drive features (30a, 30b, 30c, and 30d) are provided on opposite sides of the drive shaft 12, the first drive surfaces (30a and 30b) form one diametrically opposed pair and the second drive surfaces (30d and 30c) form another diametrically opposed pair; a pumping element having a central opening in which a portion of the drive shaft with the drive surfaces (30a, 30d or 30b, 30c) is received and the opening is larger than the drive shaft to provide a clearance between the opening and the portion of the drive shaft received in the opening ; the central opening in the pumping element having at least one planar engagement surface adapted to contact the corresponding first (30a or 30b) and second drive surfaces (30d or 30c); and the first (30a or 30b) and second (30d or 30c) drive surfaces being configured so that when the drive shaft rotates the pumping element in one direction, the first drive surface (30a or 30b) engages the engagement surface and if the drive shaft rotates the pumping element in the opposite direction, the second drive surface (30d or 30c) engages the engagement surface , characterized in that the central opening permits some relative rotary movement between the drive shaft and the pumping element of up to 45° relative to the axis of rotation and when the engagement surface is engaged by either the first drive surface (30a or 30b) or the second drive surface (30d or 30c), the surface area of engagement between them is 0.3 mm 2 to 3 mm 2 . a drive shaft having an axis of rotation , driven for rotation in at least one direction, the drive shaft having at least one planar first drive surface (30a or 30b) formed on a portion of the length of the drive shaft, at least one planar second drive surface (30d or 30c) formed on a portion of the length of the drive shaft, and when multiple drive features (30a, 30b, 30c, and 30d) are provided on opposite sides of the drive shaft 12, the first drive surfaces (30a and 30b) form one diametrically opposed pair and the second drive surfaces (30d and 30c) form another diametrically opposed pair; a pumping element having a central opening in which a portion of the drive shaft with the drive surfaces (30a, 30d or 30b, 30c) is received and the opening is larger than the drive shaft to provide a clearance between the opening and the portion of the drive shaft received in the opening ; the central opening in the pumping element having at least one planar engagement surface adapted to contact the corresponding first (30a or 30b) and second drive surfaces (30d or 30c); and the first (30a or 30b) and second (30d or 30c) drive surfaces being configured so that when the drive shaft rotates the pumping element in one direction, the first drive surface (30a or 30b) engages the engagement surface and if the drive shaft rotates the pumping element in the opposite direction, the second drive surface (30d or 30c) engages the engagement surface , characterized in that the central opening permits some relative rotary movement between the drive shaft and the pumping element of up to 45° relative to the axis of rotation and when the engagement surface is engaged by either the first drive surface (30a or 30b) or the second drive surface (30d or 30c), the surface area of engagement between them is 0.3 mm 2 to 3 mm 2 . <EOS>