The needle of system B-27 has a medium ball point for working knit fabrics, without damaging the stitches. The SF version has an extra-slim point and eye area for the finest knit fabrics, but without shank reinforcement and therefore more sensitive to deflection. It is used in industrial overlock, coverstitch and safety-stitch machines for elastic knit fabrics. Suitable machine classes are found, among others, at Kingtex (classes SH-7002-032-M02, SH-7003-032-M04, SH-7003-052-M04, SH-7003-053-H04), Siruba (classes 737FS-504M2-04, 737FS-504M2-04/GL, 737FS-504M2-04/LF-D6/LFAK, 737FS-504M2-04/LFC-2S) and Zoje (classes ZJ-722-02X250-BD, ZJ-722-02×250, ZJ-722-02×250-BD, ZJ-732-355).
Thinner needle sizes are used, among others, for fine, light jersey and tricot fabrics, and the thicker versions for heavy, dense knit fabrics and technical knits. As sewing thread, a matching thickness is usually recommended depending on the needle size chosen, e.g. from Amann Serafil or Rasant; for very stretchy seams, a texturised thread also works well. The ball point glides between the loops instead of piercing them, keeping the seam clean and undamaged.
