This model is the latest product of compound feed lockstitcher (Double needle), which is designed with large vertical rotating hook (Specially for thick thread) for thread loop catching and sliding bar for thread up-taking. The application of the needle bearings for arm shaft and hook shaft, cog belt driving, plunger oil pump for automatic lubrication. Compound feeding by needle bar, presser foot and feed dog provides this series with such splendid features as smooth funning, quiet working and long service life. It is also equipped with a safety clutch to prevent the hook from damage by over-duty operation. This machine is derived from 4400, which increased the working space (330mm X125mm), it will sew 20 plies twisted thread at maximum, the stitch length gets to 12mm/needle. So it is especially available in stitching carseats, safety belts, safety air bags, tents, parachutes, mat, sails, etc.