4" Vent - Typically used on USP Eight Cox FootStop & Stern Sectional 4's.

5" Vent - Standard use in all SP HUDSON Singles through to Eights, USP Singles, Pair/Doubles & Fours. Now with improved seal & 1/4 turn lock.

6" Vent - Standard use in all USP 8's Now with improved seal & 1/4 turn lock.