Tom The Cokin Mount ccme in two main sizes: A series (for lenses with a filter thread of 36-62mm) P Series (for lenses with a filter thread of 48-82mm) There are also x pro and z pro series, no need to mention theme here. The P series will probably cover all the more common lenses. Cost: Not too bad, basic set up approx 20-30 GBP so probably about the same in USD?! What you must have is the filter holder and a lens adapter in the diameter of the lens. The filters are all sold separately and the cost depends on the type of filter, in the same way the screw in filters do. There are some starter sets available which include the filter holder and two or three filters, the lens adapter will depend on the lens thread diameter. For example if your lens has a 58mm thread then you need the 58mm adapter, the lens adapters are interchangeable so if you have 3 lenses, say, 58mm a 67mm and a 77mm you need three corresponding lens adapters, but the lens holder and filters will fit them all when you change the lens adapter ring. OMG hope that all makes sense. Anyway it is a very versatile system that you can add to as you need/want to. Yes it does take a bit more tome to set up a shot using this system; I guess that is a pros and cons issue. IMO worth the effort. Simon

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