Though the UV filter which has the transmission shorter than 300nm is not common for ground-based telescopes, it is sometimes requested for a wide field UV telescope based on CubeSat platform.
It is technically very hard for any vendors to fabricate the UV transmission filter which transmits shorter than 300nm and blocks ~ 700nm or longer due to the property of coating materials.
We succeeded in coating a prototype of the UV transmission filter by our proprietary magnetron sputtering technology.
Maximum 200mm diameter is now available.