There are so many different names for these uppers but the common shared feature is these do not have the standard external threading for a barrel nut upon which a handguard would attach. In the LMT case the upper and handguard are one piece; for the others the front of the receiver extrudes forward where the barrel and barrel nut fits inside the upper while the handguard attaches to the outside of the upper receiver itself. I‘ve read some of the justifications for these designs: better hand-guard rigidity for holding zero, decreased handguard leverage induced POI shift, and others I don’t understand enough to even parrot. I’ve also read opposing points of view: loss of handguard compatibility, POI reduction insignificant, proprietary barrel extensions in some cases. I’m not really looking to be convinced or dissuaded from getting one of these uppers - for better or worse I want a rifle with this design. However I’m also not the best at choosing between very similar options, so if you all were considering a rifle with this upper design which of poll choices would you choose and why? Currently I’m sitting between the LWRCI IC-DI and LMT MRP-L MLOK and making no headway.