These steel cupped heat shields go under the rubber mounts to help deflect heat and grease away. In most cases (unless your engine is severely shaking) they will prolong the life of the rubber mounts. These shields attach to the T-shaped bracket this is mounted on the intake manifold of most 5 cylinder turbo diesel engines.
These can help prolong the lift of the rubber mounts under your air cleaner housing
617 Turbo Diesel Air Cleaner Rubber Mount Heat Shields ( Set of 3 )