Schmetz say:

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The CF in the needle designation stands for Chrome Finish. This means that the needles are coated with chrome.

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For household overlock or coverlock machines whose operating instructions specify the use of the needle system ELx705, ELx705 CF, ELx705 CR or SY 2022.
Flat shank, Overlock Needles with a second thread groove to create chain stitches such as overlock or coverlock

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It has a medium ball point, making it perfect for knitted fabrics, such as jersey or sweatshirt fabrics.

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