Attached Link: http://www.cokin.fr/ico1-p2.html

What's the code on the filter's box ? (A, P, X-Pro, etc) Cokin's a great system, and it goes like this: You need a holder that will hold the filters. Then you need an adapter ring, for every lens diameter and you screw it on the lens....the holder slides on the ring. The A, P and X-Pro are 3 different holders, A is smallest, etc....like for medium and large format cameras you use X-Pro, for wide angles and lenses with large diameters you use P, for all the other normal (smaller) lenses you can use A. So you should get a holder and ring/rings that match your equipment, and match whatever type of filters you got (like I said either A, P or X-Pro size). Well, have a look at the link for their site :) And about the filters themselves, I guess they are spot in filters, cause I understand only the center figure is clear/transparent, right !? Well, if they are you are correct...they are for portraits, or just anything else when you want to blur everything except the middle of the picture. I guess they work best for portraits though....but I hardly ever find them usefull (but that's just depends on what you shoot :), cause I think the ones I have -with just a circle- are too strong. What I do like a lot is a diffuser filter from Cokin, cause especially when used with reflections in water it looks really nice. Err...I'm busy writing a little tutorial on filters for renderosity and I think I already made some shots with and without diffuser. Lemme see.