Every now and then spools of thread will go a bit wobbly! The spool stabilizer and cap set is just th ecure. The four winged spool stabilizers are perfect for stabilizing any large cone thread. Just slip over top of your spool pin. When you place the cone thread over the spool stabilizer, the four rubber wings grip the inside of the cone and NO MORE WOBBLE!. The set also includes 6 small and 6 large spool caps. Thse prevent smaller spools from wobbling and lead the thread off the top of the spool so you will never agan break your thread due to backlash.