Pack of 30 Schmetz Industrial Overlock Sewing Machine Needles. Needle System : B-27 Equivalent needle system numbers : 1886, 88X1, B27, DCX1, DCX27, RIM27, RMX27, MY1023, SY6120, UY191GS These are round shank needles for industrial overlock machines. Will not work on home portable sergers. Schmetz B-27 needles are available in following sizes. Please select your size. Singer Size 9 (Metric Size 65) Singer Size 10 (Metric Size 70) Singer Size 11 (Metric Size 75) Singer Size 12 (Metric Size 80) Singer Size 14 (Metric Size 90) Singer Size 16 (Metric Size 100) Singer Size 18 (Metric Size 110) Singer Size 19 (Metric Size 120) Singer Size 20 (Metric Size 125) Singer Size 21 (Metric Size 130) Singer Size 22 (Metric Size 140) Lower size numbers are narrower or thinner needles used for lighter materials. Higher size numbers indicate a needle of thicker diameter, used for heavier materials. Match your needle system to your machine, then the size of the needle to the product you are sewing.