Faria 4" Gauge Engine Synchronizer f/Dual Engines Gas & Diesel Cleats The captive hex nut is

The captive hex nut is a great feature for underwater installations

Heavy duty Solid Stainless Steel cabinet and door built to last in harsh marine environments

but that doesn't mean it doesn't need to be polished & sealed

PropGlide™ is available in four easy-to-use size kits

Faria 4" Gauge Engine Synchronizer f/Dual Engines Gas & Diesel Cleats The captive hex nut is4" Gauge Engine Synchronizer for Dual Engines Gas & Diesel Hole Size: 4" Features: Perimeter lighted dial Measurements in standard and metric units with icons For Gas and Diesel Dual Engines This product may not be returned to the original point of purchase. Please contact the manufacturer directly with any issues or concerns.