12×9 BOLT System with Adjustable Upper HingeProperly sized trim tabs improve the performance of your boat by adjusting the running angle of your vessel. Bennett Marine trim tabs help you get on plane faster, correct listing (roll), improve visibility, and increase overall efficiency and control.Features:Get on plane quickly to see over the bowIncrease vessel performance and efficiencyCorrect listing (roll)Adjust the boat’s attitude for changes in speed, sea conditions, and shifting weightCorrect porpoising (rhythmic bouncing)Controls sold separately General guidelines for choosing a trim tab size:In general, the widest span tabs that will fit on the transom will be the most effective. The greater the surface area, the greater the lift. We‘ll typically recommend a 9” chord tab, but depending on available transom space a shorter or longer chord tab, or specially shaped tabs with upfins or dropfins may be advised.As a general rule for boats with max speeds of 40MPH, choose at least one inch of trim tab span (per side) for every foot of boat length. For example, a 22′ boat would use a 24”x9”.For speeds 40MPH and over, we’ll generally point you to one of our Performance, or Premier Line high-performance systems.This product may not be returned to the original point of purchase. Please contact the manufacturer directly with any issues or concerns.