Sierra STT3133R Standard 12 x 12 Trim Tab Kit 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. An auto-retract feature activates in situations such as shift moving to reverse. The kit comes with all hardware needed to mount your new trim