Sierra STT3207R Edge Mount 12 x 9 Electric Trim Tab Kit wController These trim tabs feature an edge mount tabs with a intuitive dial controller with one touch buttons for smooth operation. These Sierra Trim Tabs are made of 12 gauge 304 stainless steel with the stainless finish for extreme durability in marine environments. Trim tabs make the single most important difference in the way your boat rides and performs. They are optional on some boats but should be as standard as power trim and tilt.