Small Car say,

This light panel upgrade replaces your stock circuit board with a Small Car designed LED equipped panel for clear white and green filtered light and extra brightness. This also allows eliminating the bleeding that normally happens with these boards giving absolute clarity at a glance to the status of your differential. The board fits into your existing differential housing and uses the stock wiring plug.

CVC say,

Just one more part exclusively offered here in the UK and Europe from your favourate Syncro parts suppler to complete that missing link in the Syncro diff lock system.