A carrier arm assembly for an operating unit of an agricultural machine includes a carrier arm having a base part and an extending part that is telescopically adjustable relative to the base part to adjust the length of the carrier arm between an unextended configuration and an extended configuration. The base part and the extending part both include a set of bearing surfaces that are configured to enable sliding movement of the extending part relative to the base part. The bearing surfaces of the base part include upper inclined bearing surfaces and lower inclined bearing surfaces, and the bearing surfaces of the extending part include upper inclined bearing surfaces and lower inclined bearing surfaces, which are configured to engage respectively the upper inclined bearing surfaces and the lower inclined bearing surfaces of the base part.
