M2 is designed to support up to 300mm F2.8 lenses.
Field tests show it indeed works well.
Dennis Biela tested M2 with Sony 300mm f2.8 G MKII on A99 with battery wrip.
And he loves it.
So M2 will support any lens up to 300mm F2.8, 400mm F4.Originally Posted by Dennis Biela
500mm or 600mm can be supported by using dual vertical arm and longer lower rail.