I wanted a simple frame to hold a mini hydrometer to a spool to save drilling holes in storage containers and to enable me to hold the hydrometer in a position where it could be seen in a storage bag.  I have created 2 versions with different widths between the ‘prongs’ that hold the sensor to the spool as i found spools differ.  Since this i have realised that you can heat the outer with a heat gun or gently with a lighter and then flex it in slightly to increase the grip if necessary