Received this 100mm plastic vent diffuser in 67 days. The difference between this model and most others: 1. less curvy desing (more angled edges) - not a problem, it's a matter of taste, 2. insufficient edge smoothing and no final touches - it's a pitty because this could have been easily avoided with some quality control in the factory, 3. the threaded shaft is plastic, not metal, and there is no nut on it (so you can't limit how far to unscrew the central part for better airflow) - plastic will wear out more quickly. Conclusion: not too bad but should be a USD $1 cheaper for all the inferior details.
150 mm version fits ideally to 180 mm ventilation pipe. Fast delivery.