A feedback system for a rotating component (24, 28; 602) of an aircraft engine, the rotating component (24, 28; 602) rotatable about a longitudinal axis, the system comprising: a feedback device (204; 204') configured to be coupled to rotate with the rotating component (24, 28; 602) about the longitudinal axis, the feedback device (204; 204') comprising: a body (302; 302'; 606) having a plurality of cavities defined therein and circumferentially spaced thereabout, each of the plurality of cavities configured to receive therein one of a plurality of position markers (306; 306'), the body (302; 302'; 606) made of a non-ferromagnetic material and the plurality of position markers (306; 306') comprising a ferromagnetic material, and a sealing member (304; 304') configured to be secured to the body (302; 302'; 606) for retaining the plurality of position markers (306; 306') within the plurality of cavities; at least one sensor configured for producing, as the feedback device (204; 204') rotates about the longitudinal axis, at least one sensor signal in response to detecting passage of the plurality of position markers (306; 306'); and a processing unit communicatively coupled to the at least one sensor and configured to determine a rotational speed of the rotating component (24, 28; 602) from the at least one sensor signal received from the at least one sensor, characterised in that: the body (302; 302'; 606) comprises an outer surface and an inner surface opposite the outer surface, the plurality of cavities (306; 306') extending from the inner surface towards the outer surface and the plurality of position markers (306; 306') configured to be inserted into the plurality of cavities through the inner surface, wherein the sealing member (304; 304') is configured to be secured to the inner surface of the body (302; 302'; 606) for retaining the plurality of position markers (306; 306') within the plurality of cavities, and further comprising an adhesive disposed within the plurality of cavities for retaining the plurality of position markers (306; 306') therein. a feedback device (204; 204') configured to be coupled to rotate with the rotating component (24, 28; 602) about the longitudinal axis, the feedback device (204; 204') comprising: a body (302; 302'; 606) having a plurality of cavities defined therein and circumferentially spaced thereabout, each of the plurality of cavities configured to receive therein one of a plurality of position markers (306; 306'), the body (302; 302'; 606) made of a non-ferromagnetic material and the plurality of position markers (306; 306') comprising a ferromagnetic material, and a sealing member (304; 304') configured to be secured to the body (302; 302'; 606) for retaining the plurality of position markers (306; 306') within the plurality of cavities; a body (302; 302'; 606) having a plurality of cavities defined therein and circumferentially spaced thereabout, each of the plurality of cavities configured to receive therein one of a plurality of position markers (306; 306'), the body (302; 302'; 606) made of a non-ferromagnetic material and the plurality of position markers (306; 306') comprising a ferromagnetic material, and a sealing member (304; 304') configured to be secured to the body (302; 302'; 606) for retaining the plurality of position markers (306; 306') within the plurality of cavities; at least one sensor configured for producing, as the feedback device (204; 204') rotates about the longitudinal axis, at least one sensor signal in response to detecting passage of the plurality of position markers (306; 306'); and a processing unit communicatively coupled to the at least one sensor and configured to determine a rotational speed of the rotating component (24, 28; 602) from the at least one sensor signal received from the at least one sensor,