I got the TrusMT mattebox special deal a few months ago and have bought some Formatt filters to go along with them. ND filters and a circular polarizer. You get an idea of what these filters do in the clip I made. Curious to hear/see what other 4x4 filters are used with the (new) matteboxes. Formatt is not cheap but I believe it's the cheapest glass that also has a good reputation. A guy from England on eBay sells them for around €60,- a piece, which is not bad. http://tinyurl.com/6bjhxzg