This is an adapter that will let you use a 3/8" bolt on your rhino rack. This will allow you to tighten a bolt in the rack. You can use any length bolt depending on what you are mounting. Made this for my Pioneer Roof Rack as I was sick of paying the high price for brand name mounts. These are a TIGHT fit, you will need to gently tap the bolt in with a rubber mallet or the like.