Abstract: This invention is directed to a fluid pump containing a structural member, such as casing, which the fluid contacts as it enters the pump, and to a structural member having sufficient mechanical strength and flexibility for use in a fluid pump, such as a casing, which is made of a ring-opened polymer of a norbornene-type monomer containing an effective amount of an elastomer, the structural member has heat distortion temperature of over 120.degree. C., elongation at break of 15 to 80%, and flexural modulus of elasticity of 170 kg/mm.sup.2 or above.