Probably wrong but i thought the casing was smaller on the old style one.
I have the new style but the black plastic one i am upgrading to the Netoptic and i got all the bits and the Netoptic cup holder was the old style and iam shore the casing were different between the new and old because i wanted to have the new style holders with the Netoptic but i am having to get a new style holder with Netoptic when i can, but like i siad i could be wrong