Hi Cal and welcome. Halo Scopes are normally associated with Night Vision / Thermal Scopes. Is this what you mean? If so, any would work, you just need to determine the specifications you want. It will mount directly to the Top Picatinny Rail with the Picatinny Mount. Cheers, stay safe and enjoy!

Cal, this uses a picatinny rail to attach optics. So any picatinny style optic/mounts will work. Personally I prefer lpvo/low power variable optics for AR-15s. If interested here's a link to a 1-4 magnification scope id recommend and comes with everything you need to mount it to this..................... budsgunshop.com/product_info.php/products_id/5007/truglo+tg8514bc+tru-brite+1-4x+24mm+obj+92.6-23.03+ft+@+100+yds+fov+30mm+tube+b ........................ If you prefer a one piece scope mount instead of scope rings here's another option also includes everything needed.................... budsgunshop.com/product_info.php/products_id/5019/trutg8514bt+tact+ar+sc+1-4x24 ...................... If you have something else in mind just post again with little more detail on what your looking for and we can point you in the right direction. Hope this helps.

Nothing special to do as it would mount directly on top of the piccatinny rail.