I have a d16y7, I bought it from a friend and he had the JRSC set up all half a$$3d.
He had the stock belt on it so it wasnt using the lower idler pulley. I put a new alternator and the right belt on it but now my lower idler pulley is sticking out to far about an 1/8", I don't even know if it is the right pulley or not so I need your guys' help to determine if It is the right one or not and what I need to do to get it to line up so it doesn't eat my belt, and where I can get a new pulley if it is not the right one.. The top one isn't slotted but the bottom one is, Here are some pics.

 

It's not supposed to be slotted at all, it's worn out that bad!

You need to order another one from Moss.

 

youned a new pulley that true
but the cause of the problem is alignment
if you take the pulley off you wil find a spacer at the back this might not be the right one or has been spaced out further with a washer
pm me your email if you would like a copy of the install instruction in PDF so you can align all the pulleys correctly as it most inportant for belt life
this will also stop slipping and pulley wear like you have

 

wow, ive never seen one worn out like that before

 

JRSC Jackson Racing Custom Idler Pulley 051-627 Prelude RSX Miata SVT Integra | eBay

Here's a direct fit aluminum one. Never need to replace it again, just swap the bearings.

 

The pulley the OP has pictured IS Aluminum. The replacement will not last forever. The belt witness mark on the pulley does in fact cut into the pulley inboard from center, but this really isn't an issue. As long as it isn't rubbing against the front or rear lip... you will be fine. Focus on proper belt tension once you replace the pulley and belts should last 30K miles or so.