A few weeks ago I requested a free sample of ready-wound bobbins from Fil-Tec Bobbin Central. Tonight I am using my first one and I love it! I took the check spring out of my bobbin case as the Magna-Glide has a magnetic core. This is a polyester bobbin and I'm using PermaCore on top. No adjustments were needed and I love the look of it. I will be ordering a supply of these soon.