All steel, matte black. Inside nubs for 17" & 18" caps is 7". Inside nubs for 20" & 22" caps is 7 1/2". C52 cap included with all wheel sizes and is the only cap that fits 20". Lug nuts not included. A reverse rim is used for 513-8010400 to achieve backspace. These are dual bolt pattern wheels, with 10 bolt holes. Please note that 17" & 18" options have a ring around the hubcap area, the 20" & 22" options do not (see photos). Doesn't fit Jeep Samurai.