The Husqvarna Viking Amber Air S400 makes threading your overlocker a breeze! Simply thread the lower and upper loopers at the touch of a button. And the ease of use does not stop there as the Amber Air S400 has a built-in needle threader which will thread both the left and right needles with a slight adjustment between needles. The electronic speel limiter allows speed control up to 1,300 stitches per minute. Built-in Needle Threader. Easily thread both the right and left position needles with the adjustable built-in needle threader. Differential Feed. Eliminates stretching of knit fabrics, puckering of lightweight fabrics, and can automatically gather fabric. LED Lighting. Illuminates the sewing area for clear visibility to reduce eye strain. Lay-in Tension. Easily place your threads in the tension discs and clearly see that the threads are securely in the tensions. Adjustable Stiitch Length, Cudding Width & Presser Foot Pressure. Easily place your threads in the tension discs and clearly see that the threads are securely in the tensions.