St is all steel, no aluminum..... I did some testing on them shooting concreteblock and steel drums. Not one blade broke or went out of alignment, got dull but that will happen to just about any heads shooting into bricks and steel. Shot the ST head on the concrete block5 times and5 times on the steel drum nothing happen except dull blades anda bluntedtip. I'm pretty sure if I used the same head on a deerit will break some bone easily. Not to mention that same head still flew like my field points after the testing. I'm not trying to bash on Muzzybut it failed my test andbenta blade pretty bad when shooting into thethe steel drumand on the second shot I shot at the concrete block and the muzzy's tip broke, I though it was just because I shot at the steel drum first but put on a new muzzy and shot at the block and the tip bent pretty bad and look like it almost broke, that was the MAx-4. Slick tricks is one of the toughest heads out there right now. I was shooting my Ross set at 26" DL,70lbs, going about 260FPS.