This gives every non-robot companion every damage-related perk at max rank. Rifleman, Heavy Gunner, etc.
It also improves their accuracy significantly, gives them infinite ammo, unbreakable PA and no fall damage. It also modifies all their outfits to have a damage resistance equal to Ballistic Weave MK.5 (Minus Deacon and Curie). In some situations these guys might be able to show you up in a gunfight