I absolutely love my x-pen; like everyone already said top is a must. My first introduction to basenji escaping was my little 10week old puppy making his way up over the exercise pen. I made the mistake of not buying the top from the get-go, and didn't get one with a door on it consequently; now my pen is all warped and bent out of shape.
FYI the clips that come with the Midwest pens are POS, my dog ended up warping a lot of them….so I'd buy some better clips. I bought both crate and top off Amazon as well. The crate is a good deal in my opinion. The crate has been great, but the tops are overpriced in my opinion....
X-pens are fantastic, but they are easier to escape from than a crate.... learned that lesson the hard way when Beo managed to dig under the carpet and squeeze underneath it - while scratching up his underside in the process. A small puppy should have no problem though...
24 x 30 is what I got. No complaints.