6061 T6. I was thinking about the 7075, but didn't go with it. I think that was the right move. A couple people on here who know a lot more than me about it have said that the 6061 is plenty strong and the 7075 is a pain to work with.
This was pretty easy to work with. I used a regular Dremel cutting bit for plastic and soft metal and my regular drill bits. I also used a kid size bargain hacksaw and bargain set of hand files with no complaints.