Cutting line / line feeding, your trimmer uses.065 inch (1.65 mm) diameter, round nylon line.
Question: Spool Cap W/spring For GH700/710.
It lost some power and dropping small bearings.
Cutting line will wear faster and require more feeding if the cutting or edging is done along sidewalks or other abrasive surfaces or heavier weeds are being cut.
Grasp empty spool (d) with one hand and spool housing with other hand and pull spool out.
The advanced automatic line feeding mechanism senses when more cutting line is needed and feeds and trims the correct length of line whenever its required.