A M1/8 x 27 – F3/8 x 24UNF elbow is a brass or steel adapter used to connect brake lines and other automotive parts. It is a 90-degree elbow fitting with a male 1/8-inch x 27 NPT (National Pipe Thread) connection on one end and a female 3/8-inch x 24 UNF (Unified National Fine) inverted flare connection on the other.Â