Seadog Exhaust Thru-Hull 3" S/S 521130 by Seadog $82.07 1 2 3 4 5 6 7 8 9 10+ Quantity Quantity Add to cart Seadog Exhaust Thru-Hull #354-521130 Cast 316 Stainless Steel Flap with Rubber Seal. Size: 3" x 5-7/8".