This harness will enable LED DRL when headlights are on.
Note: this product is designed to work only with LED DRL option (MX-5 GT/Club trims)
Available configurations (using jumper):
"with brightness control" - reduced brightness when headlights are on (night mode) and full brightness if headlights are off (day time) - without jumper.
"without brightness control" - when jumper is installed.
Plug-n-Play installation between the ESU and DRL/Headlight cable.
Designed and produced by MX5things.
More details in the blog post and Miata forum