The SM600 and the SM420 are basically the same unit, however the SM420 is mostly used on vineyards as this suits the row spacing. The dimension that you need to know to check which model suits your spacing is from the centre of the top link (being the centre line of the tractor) and the outside of the block when the sidemount unit is retracted into the transport position.
SM600 1235mm from centre of top link to outside of block (2100mm overall width)
SM420 1140mm from centre of top link to outside of block (1800mm overall width)
The photo below shows the SM420 with a Mule post diver and the Rock Spike Extractor.The photo does not show the lockable toolbox, however it is included.
