I believe this is the one you need. This is the kit shown on the Lawn-Boy parts site.

ebay # 281084527644

saxman1:
Are you fairly confident this one will work with my model 10515. I called lawn-boy but they were no help at all. The actual bagger that came with the mower when I bought it was a side bagger. I later bought a rear bagger (which got lost when I moved). So, I am trying to find another rear bagger. SInce the side bagger is the bagger that came with the mower, that's what the owners/parts manual shows. It does not tell me if any of the rear baggers will work although the one I had did.

This is the kit shown on the LB site for the bagging set for the 10515, and this kit is labeled 'for all LB mowers with offset front wheel'.

Thanks again. I'm taking my 10515 to the shop to get fixed and then I will purchase bagger for it.

The kit you are looking at may work, but it is considerably different from any Lawnboy rear bag that I've ever had and I have had three of them. You might want to look at the rear bag kit they sell on Amazon (Lawnboy 89906). Those are what my rear bag kit looked like.