Overall good product, but NOT dust proof as delivered: the diaphragm body is only loosely inserted into the PP frame, but neither glued nor sealed. I will try to glue it tight, but that will be difficult to do since PP is not easily glueable. Additionally, both threads into the brass nut are also not sealed; but I'm confident that can be rectified using a bit of PTFE sealing tape.
Havent tested it yet, but seems like good building quality.