Originally Posted By AR15fan:
California law does not require that the magazine "block" be permanantly installed.
This is very debatable. Most cautious users ensure that magazines cannot easily (by hand or with simple tools) be converted to their original capacities.
Still, Magpul's approach with these 'limiters' is an excellent one. For those states which don't require permanent modification (but perhaps require 5-round mags for hunting), these can easily be swapped in and out. For states like California - and for the more cautious users - these can be installed and the floorplate then epoxied or riveted to achieve permanence of modification.
Plus, it lets us create limited-capacity mags in FDE, OD, and foliage...not just black.