Yes it is deffinatly worth getting. It is a billet adaptor that you bolt in to the air box. Then you have a filter with dual flanges that use hose clamps to secure it to the billet adaptor. It seals up way better than the drop in K&N replacement filters. You dont have to rely on the air box lid to hold the filter in place. You can run with out the air box lid at all.I was looking for info about cheaper air filters, what adapter is this? The YA-6601 is running about $50... is it really worth getting an adapter?