A mandrel for an elastomeric pump, comprising: a body extending over a length (L M ) from a first end to an opposing second end ; an outer diameter (D M ); a bore extending within the body; an inlet port defined near the first end , the inlet port in fluid communication with the bore ; a fill port defined between the first end and the second end , the fill port in fluid communication with the bore ; and a means at the first and second ends to secure an elastomeric bladder over said mandrel , characterised in that : the outer diameter (D M ) at the midpoint (M M ) of the length is less than the outer diameter at each of the first end and the second end such that the mandrel is a generally concave mandrel; or the outer diameter (D M ) at the midpoint (M M ) of the length is greater than the outer diameter at the first end and is less than the outer diameter at the second end such that the mandrel is generally tapered from the second end to the first end, wherein the fill port is defined near the first end ; or the outer diameter (D M ) at the midpoint (M M ) of the length is less than the outer diameter at the first end and is greater than the outer diameter at the second end such that the mandrel is generally tapered from the first end to the second end, wherein the fill port is defined near the second end . a body extending over a length (L M ) from a first end to an opposing second end ; an outer diameter (D M ); a bore extending within the body; an inlet port defined near the first end , the inlet port in fluid communication with the bore ; a fill port defined between the first end and the second end , the fill port in fluid communication with the bore ; and a means at the first and second ends to secure an elastomeric bladder over said mandrel , characterised in that : the outer diameter (D M ) at the midpoint (M M ) of the length is less than the outer diameter at each of the first end and the second end such that the mandrel is a generally concave mandrel; or the outer diameter (D M ) at the midpoint (M M ) of the length is greater than the outer diameter at the first end and is less than the outer diameter at the second end such that the mandrel is generally tapered from the second end to the first end, wherein the fill port is defined near the first end ; or the outer diameter (D M ) at the midpoint (M M ) of the length is less than the outer diameter at the first end and is greater than the outer diameter at the second end such that the mandrel is generally tapered from the first end to the second end, wherein the fill port is defined near the second end . the outer diameter (D M ) at the midpoint (M M ) of the length is less than the outer diameter at each of the first end and the second end such that the mandrel is a generally concave mandrel; or the outer diameter (D M ) at the midpoint (M M ) of the length is greater than the outer diameter at the first end and is less than the outer diameter at the second end such that the mandrel is generally tapered from the second end to the first end, wherein the fill port is defined near the first end ; or the outer diameter (D M ) at the midpoint (M M ) of the length is less than the outer diameter at the first end and is greater than the outer diameter at the second end such that the mandrel is generally tapered from the first end to the second end, wherein the fill port is defined near the second end . <EOS>