Stainless steel, while harder to machine than aluminum is infinitely more durable. We are pleased to offer our solvent trap designed for all the crud your AR15 can throw at it. Threaded in half by 28 threads the trap will go on any American made .223/5.56 barrel made in America. It will also go on most .22 LR caliber pistols and rifles. the body is made of 6061-t6 aluminum and the cones are made of 304 stainless. All the solid parts are center marked.