1,It use big roller instead of three smaller ones,so the groove is straight. 2,The slotting angle can be adustable 3,V groove Purpose And PerformanceGrooving Machine for cardboard slot1,Environmental protection, no noise and no dust, also the wastage can be recyclable.2,Effect:The groove is very smoothly.3,Convenience:this machine is very easy operation, you can put in any place, and no need ...