A wear sensing liner for a comminution apparatus , the wear sensing liner comprising: a liner body comprising; a wear surface side defining a wear surface; an opposed, operatively rear surface side ; and at least one sensor carried by the liner body , the at least one sensor being carried by the liner body to sense wear of the wear surface side of the liner body , the at least one sensor being configured to degrade in response to wear of the wear surface side of the liner body and to output a signal representative of the wear of the wear surface side of the liner body; wherein the at least one sensor comprises a rigid sleeve configured to mount the at least one sensor to the liner body, and characterised in that : the liner body comprises an insert which partially spans the depth of the liner body or span the entire depth of the liner body, wherein the liner body is formed of a castable material cast around the insert and wherein the insert has a higher melting temperature than the material(s) constituting the liner body; wherein the insert is configured to receive the rigid sleeve of the at least one sensor when the at least one sensor is mounted to the liner body. a liner body comprising; a wear surface side defining a wear surface; an opposed, operatively rear surface side ; and at least one sensor carried by the liner body , the at least one sensor being carried by the liner body to sense wear of the wear surface side of the liner body , the at least one sensor being configured to degrade in response to wear of the wear surface side of the liner body and to output a signal representative of the wear of the wear surface side of the liner body; a wear surface side defining a wear surface; an opposed, operatively rear surface side ; and at least one sensor carried by the liner body , the at least one sensor being carried by the liner body to sense wear of the wear surface side of the liner body , the at least one sensor being configured to degrade in response to wear of the wear surface side of the liner body and to output a signal representative of the wear of the wear surface side of the liner body; wherein the at least one sensor comprises a rigid sleeve configured to mount the at least one sensor to the liner body, and characterised in that : the liner body comprises an insert which partially spans the depth of the liner body or span the entire depth of the liner body, wherein the liner body is formed of a castable material cast around the insert and wherein the insert has a higher melting temperature than the material(s) constituting the liner body; wherein the insert is configured to receive the rigid sleeve of the at least one sensor when the at least one sensor is mounted to the liner body. the liner body comprises an insert which partially spans the depth of the liner body or span the entire depth of the liner body, wherein the liner body is formed of a castable material cast around the insert and wherein the insert has a higher melting temperature than the material(s) constituting the liner body; wherein the insert is configured to receive the rigid sleeve of the at least one sensor when the at least one sensor is mounted to the liner body. <EOS>