Unifields are shields projected to defend against collisions, hostile conditions, and weapons fire of all kinds. Unifield shields use a variant of gravy to repel objects and refract away beams and particles. Almost nothing can penetrate a unifield with enough power behind it, with the exception of breacher munitions.
While indispensable, unifield defenses have several downsides. A unifield must completely block any frequencies of light it needs to defend against, meaning that a wide-band laser can render the defender's visual sensors useless. Unifields are also horrible energy drains, which is very bad if you're low on fuel.