As Adam wrote, the first one is the main part of the AC idler. It looks like you are missing the pulley and the bearing. The snap ring goes inside the pulley and next to the bearing. The pulley is a staggering $302 on Wilkinson's website. One of my cars had the same issue with the pulley and bearing missing. Only the bearing race remained on the shaft and the pulley was long gone. But for $12 at Autozone an idler pulley can be purchased that gets the job done. And it includes the bearing. Here it is:
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