Marv has given excellent advice. I use the Cokin P system with higher quality s quare filters from other filter manufacturers (Tiffen, Sing-Ray) that are design ed for the P system. It is an inexpensive way to hold filters in place, and you are not restricted to Cokin filters. The pricing of some filter and lens shade systems appear to be out of line with reality if all you want to do is hold a f ilter in front of your lenses (IMHO).