Was skeptical about what size I should order for my dog so I sized up and got a bigger size. I’m glad I did lol my dog is only 4lbs but he has sooo much room to roll around and play on now. I’m sure if I stayed with size 1 he would’ve had enough space also but I’d rather be safe than sorry. And as far as putting the bed together it was very simple and easy. I put it together by myself in no time. The only thing extra that you would need is a small screwdriver to attach the name plate but other than that it came with everything. Also make sure you line up the holes perfectly when screwing the bed together to get a good fit. I get compliments on how cute it is and people always ask me where did I get it from. I will definitely be purchasing again in the near future.