CXB (formerly Astrodon) 3nm Narrowband OIII Filter (Oxygen III)Notice: As of 10 16 2025 New production has been started and releases are scheduled over the next 12 month period. If the filter shows available for purchse and you can add it to your shopping cart it will be delivered to you at the next release date. If you have questions, call Cary at 916 628 8673. Status of the filter sizes are as follows: OIII 3nm 1. 25" mounted First release 11 14 25 OIII 3nm 36mm round unmounted First release 11 14 25 OIII 3nm