Corrosion resistant 316 stainless steel. Use with a collector box to facilitate air intake and exhaust. Designed with recessed louvers to create a flush vent surface area reducing possible damage to the vent as well as preventing chafing to mooring lines, fishing lines, etc. B 15-1/4" C 2-7/8" D 16-3/8" E 1/32" F 7/8" Fastener #6 RH