Designed for use in electronic multi-purpose sergers that do the overlock, cover, safety, and mock safety stitches. Machines should specifiy the ELX705 system - not suitable for use in normal home sewing & embroidery machines. Assortment size 80 and 90. 5 needles per pack. - Here's how ELX705 needles vary from home sewing needles. *Needles have a groove on the front side and back side of the blades to reduce skipped stitches. *The second long groove is necessary to create chain stitches like overlock and coverlock stitches. *They have increased strength due to a reinforced blade leading to less breakage and straighter stiches.