Elmarit e39 or e46 black or chrome


hi all,
i keep seeing dozens of versions of the 90 elmarit lense for sale. are there so many versions ? if so than whats the difference between the 90 elmarit 39e fiter size and the
e46 version and what about chrome versus black?
Is there a difference in lenth as well as weight? I know i could just go to a dealer and check this out for myself, but i'd like to be prepared for fear that i will walk out of the
store with a new lense, and im bad at making decisions on the spot.
thanks .