These Singer Ball Point (Style 2045) needles are used for sewing on knits; the rounded tip allows the needle to pass between the fabric threads by separating them. Sheer to Lightweight Knits 80/11: Jersey, Single Knit, Spandex, Tricot Medium to Heavy-weight Knits 90/14 or 100/16: Double Knit, Sweatshirt, Sweater Knit (Using a regular point needle on knit fabric will result in skipped stitches and fabric damage, causing it to curl.) They are compatible with the following Singer sewing machines:- M2105, Confidence 7640, Patchwork Plus C5985Q and Heavy Duty 4423