The Magpul M-LOK AFG MAG598 is ~3.9 inches long. Both medium NcSTAR Picatinny Adapter MLOKs (2-slot and 3-slot) are 3.5 inches long, and would provide a stable platform; HOWEVER, there appears to be, from looking at pictures (ie not in-hand), a misalignment issue, with both adapters’ slots and the AFG’s MLOK screws AND recoil tabs, so that the AFG can NOT be centered (ie the AFG would overhang the adapter on one end). So the best choice to try (it’s returnable) would be the 5 inch LONG NcSTAR Adapter, as it appears, again, from only looking at pictures, that the slots, screws, and tabs COULD be aligned. Other options are Magpul’s direct Picatinny AFGs, the AFG MAG411 or the AFG-2 MAG414 UPC, both MSRP $35.