A rotary steerable tool (128,828,1028) for directional drilling, comprising: a tool body (203,403,703,803,1003) including a flowbore (201,401,801,1001) for flowing pressurized fluid therethrough; a plurality of extendable members movably coupled to the tool body for selectively engaging a borehole wall, each extendable member including a piston (212,412) for moving the extendable member to an extended position; a pressurized fluid supply flow path to provide fluid pressure from the flowbore (201,401,801,1001) to the pistons (212,412); and a plurality of linear actuators (206,406,806,1006), each independently actuatable to control fluid pressure from the pressurized fluid supply flow path to a respective piston (212,412); and an insert (860,1060) removably securable within the tool body (203,403,703,803,1003) comprises at least one of the plurality of linear actuators (206,406,806,1006), the insert (860,1060) comprising; a flowbore inlet (870,1070) to receive fluid pressure from the pressurized fluid supply flow path; an exterior outlet (874,1074) to discharge fluid pressure out of the tool body (203,403,703,803,1003); a piston outlet (872,1072) to provide fluid pressure to the piston (212,412); and wherein the at least one of the plurality of linear actuators (206,406,806,1006) is arranged and actuatable to control fluid pressure between the flowbore inlet (870,1070), the exterior outlet (874,1074), and the piston outlet (872,1072); characterised in that the insert (860,1060) comprises at least one of an electrical connection (440,740) to receive power for the at least one of the plurality of linear actuators (206,406,806,1006) or a power source is positioned therein to provide power for the at least one of the plurality of linear actuators (206,406,806,1006). a tool body (203,403,703,803,1003) including a flowbore (201,401,801,1001) for flowing pressurized fluid therethrough; a plurality of extendable members movably coupled to the tool body for selectively engaging a borehole wall, each extendable member including a piston (212,412) for moving the extendable member to an extended position; a pressurized fluid supply flow path to provide fluid pressure from the flowbore (201,401,801,1001) to the pistons (212,412); and a plurality of linear actuators (206,406,806,1006), each independently actuatable to control fluid pressure from the pressurized fluid supply flow path to a respective piston (212,412); and an insert (860,1060) removably securable within the tool body (203,403,703,803,1003) comprises at least one of the plurality of linear actuators (206,406,806,1006), the insert (860,1060) comprising; a flowbore inlet (870,1070) to receive fluid pressure from the pressurized fluid supply flow path; an exterior outlet (874,1074) to discharge fluid pressure out of the tool body (203,403,703,803,1003); a piston outlet (872,1072) to provide fluid pressure to the piston (212,412); and wherein the at least one of the plurality of linear actuators (206,406,806,1006) is arranged and actuatable to control fluid pressure between the flowbore inlet (870,1070), the exterior outlet (874,1074), and the piston outlet (872,1072); characterised in that the insert (860,1060) comprises at least one of an electrical connection (440,740) to receive power for the at least one of the plurality of linear actuators (206,406,806,1006) or a power source is positioned therein to provide power for the at least one of the plurality of linear actuators (206,406,806,1006).