Abstract: A cartridge with an interior chamber to house a spool, the cartridge comprising a first part and a second part, each part including a panel of resilient material so as to be flexible along one panel edge, alignment means to align the first and second parts and align coupling means to releasably couple the first and second parts together, said coupling means comprising engageable complementarily toothed lug and surface means respectively on the cartridge parts and rigid legs on the panel having said lug means with shoulder means on each of said legs to engage the edges of apertures in tongues on the other cartridge part when said flexible panel edges are flexed to take up convex and concave configurations to make the legs convergent in a direction extending away from the panel having the legs and the tongues divergent in a direction extending away from the panel having the tongues, and an opening in one panel to permit driving engagement of driving means with a spool when housed in said chamber.