All steel, gloss black & chrome. Inside nubs for 17" & 18" caps is 7". Inside nubs for 20" cap is 7 1/2". C52 cap included with all wheel sizes and is the only cap that fits 20". Lug nuts not included. Please note that 17" & 18" options have a ring around the hubcap area, the 20" & 22" options do not. See Series 513 for center detail photos. A reverse rim is used for 514-8010400 to achieve backspace. Doesn't fit Jeep Samurai.