A reservoir, made from a cyclic olefin copolymer (COC), for containing a fluid for infusion into a body of a patient includes a proximal end adapted to connect to an infusion set, a distal end, a cylindrical wall longitudinally extending from the proximal end to the distal end, and a piston adapted to be slidably mounted within the reservoir at the distal end. The COC may be Topas® and the reservoir may be used to contain insulin. The piston forms a fluid tight seal and may be connected to a linear actuation member. Additionally, the piston may be formed from an elastomeric material including rubber, silicone, bromobutyl, natural synthetic isoprene, nitrile, and/or ethylene propylene diene monomers. The piston may also be made from a COC such as Topas®.