All the Details of the Bernina L850 This L850 air threaded Overlocker/Serger is the easiest serger on the market to use. You get the Free hand system knee lift. The foot pivots out of your way for ease of threading. Our needle thread works for both needles. The Loopers thread with a push of the foot pedal. As with any purchase of a Bernina we will have mastery lessons on the L850 Overlocker/Serger so that will get the most out of this serger.