4" Vent - Typically used on USP 8 Cox FootStop & Stern Sectional 4's.

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

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