MSC04601 Chevy GMC HB3/HB4 Quad 13-Pin Headlight Adapter Boss

Boss Headlight Harness #MSC04601.

This is a 13-pin harness adapter on many 1990+ Chevy/GMC vehicles and some Colorado/Canyon with four system lights.

There are several HB3/HB4 adapters so use the Boss tool to make sure this is the correct one for your application. On the plow harness end it uses and HB5 plug and on the vehicle side it has the HB3 and an HB4 plug end. 

You can find the installation instructions at this link.

To make sure this is what you need for your truck, check Boss' Power Match.