Product review (5 stars): Lower spray arm attachment.  You're a champ if you got this far.  This piece is hard to identify and locate.
Fits GE GDF520PGJBB dishwasher from Lowes.  The last couple letters might be a little different based on the date of manufacture and the color.  But if you search for the model number I mentioned and yours looks like that, it will work.  This is the piece that the lower spray arm attaches to.