Attwood Thru-Hull Connector 3/4" #23-38733 White Molded rugged plastic. Will not rust, corrode, discolor or contribute to electrolysis. Design eliminates hull streaking and allows countersinking wherever a flush fit is required. Flange OD: 1-1/4". Max hull thickness: 1-1/4" Stem: 3-1/4" NOT Recommended For Use Below Water Line.