This mattress perfectly fits my Graco Pack N Play. After reading a bunch of review last summer, I was so confused about the sizes of the mattresses and all the different names. I ended up buying the Dream on Me Portable Crib mattress for a vacation, and it fit lengthwise but was too short width-wise. I just rolled up a towel and shoved it in the gap and my son was fine. However, I just tried that with my 7 month old daughter a week ago and I woke up at 2 am with her wedged into the gap and the sheet pulled off that part of the mattress. So, I ordered the Dream on Me Pack N Play mattress and it is 2 inches wider and fits PERFECTLY. No gaps. I bought a portable crib sheet for it and that is the right size. Get this one instead of the Portable Crib mattress if you have a Graco. I'm not sure what the other 2 reviews were talking about on this product- I wish I had just bought this one last year.
I did buy a pack and play mattress, it's about 2" thick and is firm. My son wouldn't sleep in the pack and play otherwise, the pad that comes with it is not very soft or comfortable. I didn't use the mattress with the bassinet attachment but I do use it without.
For safety reasons you shouldn’t be putting any extra mattress in the bassinet, that’s the upper position of the mattress. When you not longer use the bassinet and want something softer, dream on me 3′ pack n play mattress is perfect for this playpen. You can buy it on Amazon.