Flat silk weft is a thinning form of human hair wefts. it adds double-stitched to make it firmer. Often, these flat silk weft hair extensions are thin flat, about 1mm in thickness and 10mm in width. The hair extensions are utterly safe to attach to your head as they have no silicone and are made of pure human hair. If you want hair wefts that look more invisible, Hand Tied Hair Wefts are the best choice.