I've been looking into getting a lee filter kit. I've never used these filters before but would like to learn. I've been looking in the 2filter site. Is the foundation kit just the holder? Also, what is a good ND filter to start with? I know I need to get the adapter ring. If I'm using a 24-105, should I get the wide angle adapter or just the regular one? I know I need the wide angle for my 16-35. It doesn't say on the 2filter site that the foundation kit is backordered but I've heard they are hard to get a hold of. How long is the wait? Any advice would be appreciated.