●The machine is for longer nuts that the GSN180iS can't process large diameter and longer length. ●There are 2 machines in this series. One is GSE 400i that can grind max. thread length of 400mm and the other is GSE600i that can grind max. thread length 600mm. ●There are 2 types of grinding wheel spindles available. One is quill type and the other one is spindle type.