I bought two of the large size. I like them, but they took a commitment to forge ahead with assembly. The main problem I had with both is that the plastic "T" that connects the two side pieces with each other and with the middle brace has a restricted diameter just where the two side pieces should fit together. I had to use a rubber mallet to force the piece with the larger opening in far enough to mate with the other side piece. If you hammer the piece with the smaller end in, the side with the larger end won't fit over it, so hammer in the larger diameter side piece in first. Alternatively, you could drill out the hole a little, but be careful!
Also, pay attention to how the frame fits together before you thread the end pieces into the cloth. The aforementioned "T" pieces' little holes must be oriented so the middle brace will slide in with its buttons aligned with the little holes on the "T". Good luck.