Abstract: A coupler pin couples an output sleeve of rotary unit to an input member of a rotary sensor with interference fits. The coupler pin has a first part and a second part. A key groove is formed in an inner surface of a coupling bore in the output sleeve. The first part is received by the coupling bore, and the first part has a key member which is received by the key groove. The second part has a key slot formed therein. The input member has a key. The key has a slip fit with a first part of the key slot and has an interference fit with a second part of the key slot. The key projects inwardly from a wall of a coupling bore in the input member. The second part is divided into a plurality of sections by axially extending cross-cuts.