A Crawler is a land vehicle propelled by wheels or treads that is too large to qualify as a Runner. They possess powerful reactors, incredibly dense armor, and the ability to mount tons upon tons of hardware and other systems. The most common crawlers are the heavy ore miners and mobile refineries employed in the past, and still used by low-budget operations. Some serve as land-bound dropships for Synths and other small craft, or just as cargo transports. All varieties can be converted into mobile fortresses by enterprising pirates, studding them with weaponry and armor.
Crawlers are no longer produced in any known factories. The current stock however seems to be almost endlessly repaired by whoever may purchase/steal/damage them, and still others are manufactured in private workshops from raw materials and bulk parts.
Though Crawlers were never designed to be combat vehicles, their incredible armor and ability to mount large-scale weapons should not be underestimated.