A milling tool (201o-203o) for use in a wellbore, comprising: a tubular housing ; a plurality of circumferentially aligned openings formed in the housing ; one or more pistons (210,211a,b); a plurality of arms , each arm : located within a corresponding one of the plurality of openings , moveable relative to the housing between a retracted position and an extended position, and having an inner body portion and an outer blade portion , the body portion having an actuation profile formed in one side which faces a mating guide extending from a surface of the housing , wherein the respective actuation profile and the guide are operable to move each arm radially outward as the arm is pushed longitudinally upward by the piston (210,211a,b) wherein: the milling tool (201o-203o) is movable between a deployment configuration in which said arms define the retracted position and a casing cutting configuration in which said arms define the extended position, and when the milling tool (201o-203o) is in the casing cutting configuration, the arms are in the extended position and a lateral blade sweep dimension is more than fifty percent greater than an outer diameter of the housing . a tubular housing ; a plurality of circumferentially aligned openings formed in the housing ; one or more pistons (210,211a,b); a plurality of arms , each arm : located within a corresponding one of the plurality of openings , moveable relative to the housing between a retracted position and an extended position, and having an inner body portion and an outer blade portion , the body portion having an actuation profile formed in one side which faces a mating guide extending from a surface of the housing , wherein the respective actuation profile and the guide are operable to move each arm radially outward as the arm is pushed longitudinally upward by the piston (210,211a,b) located within a corresponding one of the plurality of openings , moveable relative to the housing between a retracted position and an extended position, and having an inner body portion and an outer blade portion , the body portion having an actuation profile formed in one side which faces a mating guide extending from a surface of the housing , wherein the respective actuation profile and the guide are operable to move each arm radially outward as the arm is pushed longitudinally upward by the piston (210,211a,b) wherein: the milling tool (201o-203o) is movable between a deployment configuration in which said arms define the retracted position and a casing cutting configuration in which said arms define the extended position, and when the milling tool (201o-203o) is in the casing cutting configuration, the arms are in the extended position and a lateral blade sweep dimension is more than fifty percent greater than an outer diameter of the housing . the milling tool (201o-203o) is movable between a deployment configuration in which said arms define the retracted position and a casing cutting configuration in which said arms define the extended position, and when the milling tool (201o-203o) is in the casing cutting configuration, the arms are in the extended position and a lateral blade sweep dimension is more than fifty percent greater than an outer diameter of the housing . <EOS>