Mercury - Zero Effort R.C. Extension Harness 3-Foot Control Extension 84-8M0169399. OverviewThis three-foot extension just gives your Zero Effort control wiring a little more room to run. If the original lead is coming up short or the rigging path turns tighter than you expected, this piece makes life easier. It keeps you from forcing the harness into a bend it doesn't like or stretching it across the bay. It's a simple fix that makes the whole control line feel more natural.. Key Features • 3-F