I bought this kit because it maintains track width and offers a 25% thicker rotor than stock. The similar Wilwood's mess with track width and do not have caliper seals. The calipers are USA made, four piston, and aluminum. Obviously if you are going with a 17" wheel, I would go for a larger rotor. Myself, I prefer the look of a 15". I installed the kit on my 1965 Mustang (V8). Customer support is excellent and fast. It was my first install and went well. I am using "American" Racing Torq-Thrusts with no spacers. FYI, my spare wheel is a 1967 Mustang, plain steel, 14" - it fits perfectly with the SS4+ kit. VERY IMPORTANT - Scott Drake 15x7 Styled Steels are NOT compatible with this kit. The hub center conflicts with the center of the styled steel wheels. I am not certain about the other size Scott Drake wheels. An online review at a well known Mustang magazine showed this kit working with Magnum 500's, but I would double check thoroughly ahead of time. Baer's CS can help with templates etc. I w