Our nifty, HUGE, Lace BreakDown bobbins. These are incredibly convenient for travel and storage. Lightweight, solidly constructed, handsome bobbins are made of aluminum, acetal (Delrin), and Richlite.
To assemble the bobbins, hold the end by both sides, then insert the bobbin core and twist as you press the end onto the bobbin core. It doesn't take a lot of force, but you MUST twist while assembling.
Likewise, to disassemble, twist while pulling the end squarely away from the core. Easy!