Genuine OE knuckle joint. These joints are complete with the knuckle, nylon cup(21A423) and rubber boot(21A425). If your suspension has dropped suddenly, or you have loud squeeking noise during suspension movement, then these knuckles are one of the first things you should check. If left unchecked, the knuckle can wear through the nylon cup, into the suspension arm, and ruin the casting that supports the knuckle joint. Much cheaper than changing arms. Fits front and rear except later cars 1990 onwards with a built in spacer for extra ride height clearance.