Trimmer heads for use with a rotary powered trimming device for cutting vegetation and methods of assembling such trimmer heads are provided. A trimmer head has one or more pivoting line holders and includes a single unitary molded housing having at least one recessed cavity located on the upper surface which is shaped and sized to receive a pivoting line holder. The recessed cavity includes reinforcement members for securely retaining the pivoting line holder therein via insertion of a metal bearing ring which allows for free rotation of pivoting line holder about its central axis within recessed cavity.
