Whitecap Duplex Stainless Steel 90 Degree Thru-Hull w Barb This Whitecap Duplex Stainless Steel 90 Degree Thru-Hull is available in a variety of sizes and includes a barb. These thru-hulls are constructed of durable stainless steel that is more dense and has greater rust resistance than the traditional 316 stainless steel. Specifications Part Number Hose Size Flange O.D. Thread Length Barb Length Overall Length Cut-Out Max Hull Thickness 6576X 58 1-78 1-58 78 3-18 1-516 1-14 6577X 34 1-78 1-58 1