I can't seem to find the Thermalright APX-140 RT, is it a fearly new product? How much does it differ from the APX-140?
Dude! i gave you Thermalright's website link = contains all the possible info needed,including where to buy!
The RT replaced the previous version = universal retention hardware = that's the difference.
Support intel Socket 775 / 1366 / 1156 and AMD Socket AM2 / AM3