[RC-Monster Mike]

Aluminum is black hard anodized, while the hardened steel units are black oxide coated - both are black, though. The steel units are notably heavier(over 2x the weight) and have slightly larger radial lightening cuts on the face of the larger side. If you have a magnet, it is easy to see if you have a steel endcap. If you ordered steel, we almost certainly sent steel. :)