The Colt made ones are $15 at Brownells, and I see others going for like $3-$4, but they don't have notches on both sides so I don't think I could stake them.

What castle nuts do you use, and where do you buy them for the best price?

Thanks!

RRA or anyone else that isn't going to kill you on shipping.

There are only two designs of receiver nuts,  The first and most common is a castle nut which has wrench slots on one side and staking slots on the other.  The second type also has staking slots on one side, but no wrench slots.  It has several holes that use a spanner wrench.  This type is typically found on retro type AR/M-16's.

The ones you are looking at on Brownell's most likely have staking slots.  Got a link by chance?

Stay away from the el-cheapo lock nuts
Like High Standard http://www.brownells.com/.aspx/pid=26058/Product/EXTENSION_LOCK_NUT

Just get the $7.00 extension nut from Bravo Company

http://www.bravocompanyusa.com/Receiver-Extention-Nut-Castle-Nut-p/nut%20receiver%20extention.htm

Click link

I have never seen that thing.  Looks like a cross between the two.  OP I stand corrected, it does look like the staking slots are missing.  Like a308garand said, stay away from that one.  It's not even normal.

Thanks!    Ack, $7.95 shipping for a $7.00 part.  Damnit - maybe I'll just order the Colt one for $15 from Brownells - LOL.  Either that or find a bunch more stuff to order from Bravo :)