Matching your needle size to your thread weight makes a real difference in stitch quality. Use #70/10 for invisible thread, 60wt, and 100wt threads (ideal for appliqué and fine work). Use #80/12 for Dream Seam, Perfection, Precision, and most 50wt threads (your workhorse for piecing). Use #90/14 for Majestic, QuiltMaker, and 40wt threads when you want your quilting stitches to show. Use #100/16 for Longarm Pro, Jeans Stitch, and 30wt or heavier threads for bold, visible stitching. When in doubt, go up a needle size if your thread keeps breaking.