I've inherited a cupping kit (Daiwa) and cut it back to match the lengths of my top kits - trouble is, the diameter at the tip is too large for either the Guru rapid release or Preston Kup set (both 4mm and 5mm) to fit. My rough measuring (against a ruler) has the outside diameter at roughly 6mm or so - has anyone else had the same issue, or any suggestions, or know what size the Daiwa 'Zoom' adapter is?