I was sold on Life Like Proto 2000 wheel sets, I have no idea what material they where made from; but, they had wonderful detail and it seemed like they fit every truck I put them in. I paint and weather all wheels previous to installing in the trucks which get weathered, too. As well as not tracking dirt around the railroad and eventually derailing because the diameter of the dirt on the wheels exceeds the diameter of the flange, I love that they show bright metal on the riding surface the way real railroad wheels are burnished brightly, due to wear. Since Walthers took over the P2K brand and have now changed how; or, who manufactures the wheels, I have been messing around with various manufacturer's wheels. I don't care for the Code 88 wheel width as I find they too easily derail. This is obviously due to the fact that my track work is not perfect. So far I had been happiest with Kadee's wheel sets. They have good detail; but, now someone has said that Kadee's wheels pick-up crud, too! The last manufacturer I tried are Intermountain's and they may well be where I will stay. Walthers, deciding a change was in order (for whatever reason) for the Proto 2000 wheel-set line, was a step backwards in performance and detail! Unfortunate as it is, it killed sales of this product to me, at least.