Nissan Leaf has a design flaw that allows water to fill up the "cup" where the front dampener is bolted down to the chassis. Water just stays there, leading the bolt to rust. This is especially the case on the drivers side. Just screw this part on the bolt and you're good. It acts as an umbrella. It is not intended to be airtight, threrefore allows any water that may still manage to get in to evaporate again. Before mounting this, I had to remove the rust-water and clean the bolt since it was already starting to rust. I have this in usage now for a year and the bolt still looks like new.