Pack of 10 Groz-Beckert 151X7 Curved Serger Overlock Machine Needles. Needle System* : 151X7 151X7 needles also cross to these different needle systems : 151X5, 151X7, 60M, 60MSD, MY1151, TLX7, MRXR9 *A needle system is a group of needles made to fit specific sewing machines. All needles in a system are of the same length and shank size, but are of various diameters. 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. Orange 151X7 Needles are available in following sizes. Please select your size from the drop-down option menu. Size 11 (Metric Size 75/Merrow size 1) Size 12 (Metric Size 80/Merrow size 2) Size 14 (Metric Size 90/Merrow size 3) Size 16 (Metric Size 100/Merrow size 4) Size 18 (Metric Size 110/Merrow size 5) Size 19 (Metric Size 120/Merrow size 6) 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. Fit Singer 246, 246K, 460K Industrial Overlock Machines. Fit Merrow sergers. Needle packaing may vary.