For installation on an DPMS pattern upper, you will need the barrel nut linked below.
https://www.opticsplanet.com/aero-precision-m5e1-handguard-barrel-nut.html
This hand guard has a high profile tang for the picatinny rail. If your upper is low profile, they will not line up.
M5E1 Handguard BAR Barrel Nut Kit
They have both Aero/DPMS and armalite versions
I'm not entirely sure which one you would need, but they DO offer a barrel nut.