Does anybody know a brand of a thin, 2" threaded, Neutral Density filter? I'm putting it into a 5 position ZWO EFW and the filter body has to be less than 7mm. I have an Orion ND filter which is exactly 7mm (excluding threads) and it binds inside the filter wheel housing. ZWO says the filter housing has to be less than 7mm and the threads less than 3mm. I have a couple of other filters which are about 5mm thick and they fit perfectly. I've seen a couple other brands like Lumicon on astro web sites but they don't have specs listed.