One of our member said he could not get out the Heat Shelds till he scraped the Carbon off of the insided diameter above the heat shields.
The newest Heat Sheilds are backwards compatiable.
Simply look up your Year and Model at your favorite Parts Seller and use those.
See post #2 perhaps the Prechamber on the left in the pic is for the Top Hat type Heat Shields
http://www.peachparts.com/shopforum/diesel-discussion/337338-injector-heat-shield-removal.html
There used to be a disposable Heat Shield with a 5mm Hole and the newer ones have a 10mm Hole.
When pulled the Injectors out of My Car back in 2007 it had the Heat Shields with a 5mm Hole. The place I bought them from only sold the 5mm holed ones at that time.
Since that time they have been selling the ones with the 10mm Hole.
You can still get the ones with the 5mm Hole but you need to buy them for a VW Rabbit or Volvo Diesels from the 1980s.
No one has explained why the change was made from 5mm to 10mm.
Someone did have a good idea and said if your Injector Nozzles are used and you had the 5mm ones when you re-insall them use the 10mm ones because they will be seating on smooth unused part of the Nozzle.