peregrino - you're right, the 553 isn't in general release yet. i did a brief writeup with pics here on a pre-production model before i sent it back to eotech:
http://www.militarymorons.com/weapon...ptics.html#553
the one thing i liked better about the 553 is that it sits .25" higher than the other models (which i found a bit low on a flattop without a .25" riser like the larue mount).