Masonry Twine End Caps

These caps (2) are placed inside each end of the cardboard tube on which masonry twine is wound.  The tubes are pretty standard regarding the inside diameter, so this is one size fits most or all.  The caps prevent the twine from sliding off the end and becoming tangled, they allow stowage of the cut end of twine, and they fit over a concrete stake or similar sized dowel shaped object, to act as a spool and to allow the user to rapidly deploy twine.  The tubular piece on each cap has a chamfered outer edge, to provide for easier insertion into the cardboard tube, as this is designed to fit snugly, so they don’t fall out.  The wedge shaped slot in the larger end, allows the end of the twine to be tucked in, to eliminate unravelling.  The inside diameter measures ~19mm, the outside diameter of the tubular portion measures ~24mm, and the outside diameter of the larger end cap measures ~54mm.  Any suggestions, modifications or improvements are welcome.