This series is heavy-duty compound feed lockstitch sewing machine,which is designed with large vertical hooks for thread llop catching and sliding bar for thread take up.It has been sub-classed into single needle and double-needle.The application of needle bearings for arm shaft and hook shaft,cog belt driving,plunger pump lubrication and compoud feed by needle bar, presser foot and feed dog provides this series with such splendid features as smooth running,quiet working and a long service life.It is also equipped with a safety clutch to prevent the hooks from damage by over duty operation.So it is especially available in stitching car seats,safety belts,safety airbags,tents,parachutes, etc.