The present invention provides an actuation member for traveling down a borehole of a casing to engage with one or more geometrical profile locations provided inside the casing, and a system for controllably exposing selected locations along the wellbore to a pressurized fluid. The actuation member comprises a generally cylindrical hollow body extending between an uphole end and a downhole end, and a plug seat configured to receive a plug for blocking the borehole. The actuation member has two edge portions separate and movable relative to one another to facilitate resilient deformation of the hollow body, wherein the deformation causes a reduction of cross-sectional area of the hollow body. An outer surface of the hollow body comprises one or more protrusions and/or grooves configured to matingly engage with the one or more geometric profile locations in the casing.