question about e-code headlights... whats the diff between e1 and e4?

[JordanVw at aol.com]

im looking to get a pair of e-code 7" H4 rounds w/ citylights  (anyone have a 
nice pair for sale?)   i did find a pair (didnt buy them yet tho)  but they 
say e4 on the lens, instead of e1 that most e-codes do..   the lens is also 
slightly convex..  whats the diffrence between e1 and e4?   this pair is made by 
"Autopal" (never heard of them)..  id really like to get a pair of Hellas or 
Bosch ones but i cant find any with citylights..   

so whats the diffrence between e1 and e4?

chris