Quoted:
Mk1 has helicoil inserts for screws which require no backing plate.

IMO, the mk1 (especially the original version) is the best AR handguard ever made.

Quoted:
I am looking at an upper with a MK 1 rail and another with a MK 2 rail installed.  The upper with the MK 1 is $100 more.  From the pics and description I cannot tell the difference in the 2 rails.  In fact, both pictures look the same.

Can someone tell me the difference in them?  Thank you...!

Edit.... found my own answer on youtube,  For some reason could not insert the video directly.  Scratching head...

Click here