Use only with fine needles sizes 9-12. The "Sure Guide Needle Threader" will thread very fine needles (size 9-12). The case slides open to reveal a clever mechanism. Simply insert the needle and lay the thread in the groove. Pressing lightly on the lever directs a shaped pin into the thread through the needle eye. If the pin hits resistance it will stop, preventing it from breaking. The case will hold needles and the top has a magnet so you can easily pick up those small needles.