Cavalry Arms Mark II Lower Receiver Black
they have plenty of colors in stock. $89 ain't a bad at all for one of these.
i bought one of these for $125 just before the "panic of 08".
it seems to be a good lower, shoots fine and very light.
you save about 1lb by runig the cav arms polymer receiver/stock opposed to the regular A-1 set up.
only real negatives i have seen the the plastic-fantastic is it uses non standard take-down pins that are not captured and go in from the wrong side. and your stuck with the fixed a1 stock. not really problems but you can't put a m-4 stock on it.
be advices they fit the upper very-very tightly. so if a stiff upper to lower fit is your thing this could be your ticket.