So it can be a small beam, such as the one shot by Moiraine, or a large mass, such as the one Rand used on the Burrow. We've seen it in various forms before - when Rand directed a stream between Asmodean and Lanfear, it was a massive blast, and when he used it in other occasions, it was a more focused laser beam.

When Rand balefired the Barrow, it actually took him longer to set it up then it did in the past, because it seems that he created a massive concentration of the reality-destroying effect, and then laid it down over the entire Palace.