difference between Kappa Emit series I and series II

I blew all four Emits in my VMPS RM2 loudspeakers a while back.  All else seems to be in good order and I've been looking to replace those tweeters but find it difficult to locate the series II Kappa Emits.  I see lots of Kappa Emit-R.  What is/are the difference(s) between the 2 versions?  Any reason not to install 4 of the Emit-R tweeters instead?  Thanks.