This is the E-Flite 3" Y-Harness, Lightweight

A lightweight line of servo extension leads and a Y-harness for use with lightweight aircraft, where minimizing flying weight is important for ultimate flight performance.

Features:
Lighter gauge wire than typical extension leads
Perfect for smaller models up to park flyers
Multiple lengths available in the series: 3-, 6-, 9-, 12- and 18-inch extensions and a 3-inch Y-harness
Compatible with all common receiver and servo brands