A bobbin genie is a thin washer made out of slippery teflon. It eliminates backlash and bird's nests on the underside of FMQ. I forget to take them out, so they are in my bobbin cases 95% of the time. When I clean by bobbin case after approx. 4-5 hours of sewing & change my needle, if I'm not doing FMQ, then I take it out and pin it to my pincushion. I also use the Free Motion Slider (teflon sheet that fits over the single needle plate for FMQ). I watched Sharon Schamber do a demo in her booth at Paducah in 2008 and have been using both since then. I think there is a dozen in a pack for around $9 or $10; best money I even spent for FMQ! No affiliation, just a huge fan.