A system can comprise a plurality of containers that are coupled together as a movable unit. A plurality of container-feeding assemblies can be configured to simultaneously deliver respective yarns into respective containers of the plurality of containers. A header can be selectively attachable to a tufting machine, the header having a longitudinal axis. A retainer can be configured to extend across the header along the longitudinal axis to secure the respective yarns in respective positions relative to each other along the longitudinal axis.