On FastTech All the descriptions of April 17 are made of aluminum. In the description of the DIY version of April 18 is made of steel.
To me it seems steel, because the thickness is thin for aluminum.
looks like steel to me! They usually are better at their descriptions than most.
It’s much heavier then the other Convoy S models so it’s probably steel indeed 
Not good for heat dissapation in such a small light …