... :internal loop and External loop;Internal loop:row 1 with turn 1,like Turn x Row:1x2,1x3,1x4,1x4 ... etc.External loop,like Turn-1,Row=1.5,2.5 etc,so Turn x Row1. ... so can realize the feed(sports).Ideal applications include:1.High speed laser cutting machines2.Drilling machines3.Electronic assembly ... answer your question.Used machine and our factory 1/2 Inch Right hand ball screw by Rongter