Why the metal shrouds on the HT boots?

[Brit24]

I am just curious why the HT leads on the Octavia have this strange metal covering around the boot?

 

Why can't normal rubber boots be used?

 

Cheers

[mikec]

Metal shrouds are usually used to prevent the leads overheating

[Brit24]

Are these really necessary? the plugs don't look that deep.

Just thought about the Magnecor boots I used to have. on another car. Thick long heat resistant boots that were easy to remove.

 

Just a thought but I guess VW knew what they were doing.