All steel, gloss white. Inside nubs for 14"-16", 20" & 22" caps is 7 1/2". Inside nubs for 17" & 18" caps is 7". 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 512-8010400 to achieve backspace. Please note that 17" & 18" options have a ring around the hubcap area, the 20" & 22" options do not (see photos). See Series 513 for center detail photos. Doesn't fit Jeep Samurai.