Using deep drawn covers made of brass or aluminum and then plated with chrome, nickel or gold plating can reduce the brightness in the pickup and nickel silver is one of the best materials to be used. It is easy to draw (form in deep draw molds) and has less capacitance than brass or aluminum. In earlier VGM articles I mentioned that I removed the covers because Jeff Beck did. You could see the exposed the coils and was the reasons double cream and zebra, Gibson “Patent Applied For” humbuckers started to become collectable. I thought (along with many other guitarist) that if you had double cream humbuckers, you would sound like Jeff Beck. Someone forgot to tell us that we had to practice too! With the covers on, the pickups have maximum shielding and removing them will allow some electrical interference to be picked up by the coils.