So these bad boyz rocked up today for the Yuneec E90 Camera on the H520, going by the looks of things, if the new Yuneec C23 remains the same as shown and displayed at CES 2018, these lens filters will fit that too. Not yet tried them, but they are designed to fit the 39mm thread that the Stock U.V. filter screws on to. So no need to fit the ring adapter for using the 40.5mm camera filters. Not sure who's stocking them to be honest, im sure there will be many suppliers across the UK, States, Europe and Worldwide who will be able to supply them. There's a filter here for every scenario, from CPLs, to ND PLs, they really look the Ticket. They come in a packet with cleaning Pen and microfiber cloth, they feel nice and light and have a good quality finish. Remains to be tested, but being Freewell I'd imagine they will be pretty good Quality, Wonder if they can make the camera work better.