With their unique shape, deeper grooves and smaller diameter, sewing with PTFE thread, such as Tenara, may be improved by using these MR needles. Advertised to be stronger than conventional needle, they also reduce skipped stitches. Sold here in size MR5 which is similar to conventional needle sizes 120/19 -130/21. Fit sewing machines using System 135 x 17. Sold in a pack of 10 needles.