The 66 intake has a pair of pressed in posts, that are 3/8" between center and rear carbs. Each takes a 3/8" hose that attaches to this fitting. The fitting exits to the passenger side where a 3/8" hose runs to the PCV valve in the valley pan. This fitting was originally plactic. Heat and age have taken their toll. This one shone here is metal painted a silver color. Also have a kit on the page to replace the rubber hose from the F-fitting going back to the PCV valve.