When you want to make the most of your serging time, with professional results, the MyLock 634D is unmatched. It has 2 needles and 2, 3, or 4 thread overlock stitching. Threading is a breeze due to color-coded thread guides and an easy lower looper threading system. The MyLock 634D also lets you quickly switch to rolled hemming without changing the needle plate.2, 3, or 4 thread sergerDifferential feed ratio 0.5 to 2.25Easily accessible lower looper guidesAdjustable cutting width 3.1mm to 7.3mmMaximum speed 1,300 spmFull Features ListLay-in thread tension dials and Tension release deviceEasily accessible lower looper guidesChangeable thread guideLower looper pretension setting sliderAdjustable foot pressureAdjustable stitch length 1mm to 5mmDifferential feed ratio 0.5 to 2.25Adjustable cutting width 3.1mm to 7.3mmMaximum speed 1,300 spmWaste chip box