Its very, very tuff to get off. You must becareful to hold the gimble with 1 hand while your other hand unscrews it.
It unscrews counter clockwise. I ended up cutting my thumb on the lense. What seems to work best is get a rubber glove to get a grip on the lense. You don't have to put the glove on, just put it all over the lense, grip tight and turn counter clockwise. I used a yellow rubber cleaning glove me wife had under the sink.