ElectronGuru
Flashaholic
Can you bore a Surefire A21 extension to handle an 18mm battery?
A21's have the same issue as A19's and A14's, they are non serialized. To offer it, we would offer it to everyone. When 5 came in at once, there would be no reliable way to return each A21 back to its original owner.
If there's enough interest, we can see about offering ready made (new) ones.
Sorry,
Dan