A disc brake comprising: an actuation mechanism comprising a tappet, the tappet comprising a first formation on an outboard surface of the tappet; a disc brake rotor arranged to rotate about an axis; first and second brake pad mounting structures to be located in use adjacent opposing inboard and outboard faces respectively of the brake rotor , the second mounting structure comprising a second formation first and second brake pads located by the first and second mounting structures respectively such that upon application of the actuation mechanism the pads clamp the rotor and brake torque is reacted by the pad mounting structures; wherein the first brake pad has a corresponding first formation for interacting with the first formation of the tappet, and the second brake pad has a corresponding second formation for interacting with the second formation of the second mounting structure, wherein the first and second formations do not have mirror symmetry about a plane defined by the centre of the rotor , a radial axis R, and a circumferential direction C normal to both a rotational axis of the rotor A-A and radial axis R, and wherein to prevent or inhibit fitting of the first and second brake pads individually or in combination with friction material facing away from the rotor , the first formation of the first brake pad must interact with the corresponding first formation for the first brake pad to be fitted in the first mounting structure, and the second formation of the second brake pad must interact with the corresponding second formation for the second brake pad to be fitted in the second mounting structure. an actuation mechanism comprising a tappet, the tappet comprising a first formation on an outboard surface of the tappet; a disc brake rotor arranged to rotate about an axis; first and second brake pad mounting structures to be located in use adjacent opposing inboard and outboard faces respectively of the brake rotor , the second mounting structure comprising a second formation first and second brake pads located by the first and second mounting structures respectively such that upon application of the actuation mechanism the pads clamp the rotor and brake torque is reacted by the pad mounting structures; wherein the first brake pad has a corresponding first formation for interacting with the first formation of the tappet, and the second brake pad has a corresponding second formation for interacting with the second formation of the second mounting structure, wherein the first and second formations do not have mirror symmetry about a plane defined by the centre of the rotor , a radial axis R, and a circumferential direction C normal to both a rotational axis of the rotor A-A and radial axis R, and wherein to prevent or inhibit fitting of the first and second brake pads individually or in combination with friction material facing away from the rotor , the first formation of the first brake pad must interact with the corresponding first formation for the first brake pad to be fitted in the first mounting structure, and the second formation of the second brake pad must interact with the corresponding second formation for the second brake pad to be fitted in the second mounting structure. <EOS>