The LK150 Yarn Rod Socket is an essential part of the LK150 mid-gauge knitting machine. It comes with your new machine, but if you have lost yours, it will need to be replaced. The rod socket fits snugly into the back of the plastic needle bed and provides the place to set you needle tension mast. Positioning of the upper tension mast is important for being able to knit smoothly. 1 piece per order.