Our enclosures are made from die-cast aluminum, which is durable, light-weight, and resistant to corrosion.
Many people confuse weight with quality; a heavier object somehow feels more durable or valuable. Some pedal manufacturers take advantage of this psychological trick by "dead weighting" the enclosure. For example, some use die-cast zinc instead of aluminum. There is little difference between the material properties of these two metals (at least for their use in pedal enclosures), but zinc weighs twice as much. We have also seen dead weight added using a thick steel plate inside the enclosure.
We think that if you are carrying around a pedal board, especially a large one, you might not like this. So, we don't artificially weight our pedals.
Steel is also used by some pedal manufacturers. While stronger than aluminum, it is heavier and can rust.
For these reasons, we think that die-cast aluminum is the best choice for pedal enclosures.