This is just a heads up regarding the AR-15 upper reciever action block @ FAC.  I just recieved it and it is exactly the "Brownells - Peace River" tool, which Brownells sells for $55.  I paid $33.25 @ FAC.
The shipping is a bit more @ FAC (~$10), but if you order several items, it would even out.
For example, I also got a new USGI non-issued butstock cleaning kit for $8.50, Olympic Arms barrel multi-wrench for $22 & barrel vise jaw inserts for $12.25, etc.
http://www.gunsnstuff.net/index.html

Thanks for the info.  Do these work with all types of uppers (A1, A2, flattop)?

M4-guy,
Yes It is contoured for both the carry-handle type (A1 & A2) and the flat-top (A4), in other words, any Mil-Spec. upper.  I tried it out already and it works very well!  

I do not know wether or not the aftermarket versions such as DPMS's Low-Pro and/or High-Pro, or SOCOM's billet upper recievers will fit, seeing that they may be of thicker walled construction.

All of the other tools that I ordered worked well also.