I have get many of the Aden & Anais swaddle blanket and sleep sack . . and be delighted to find this new adorable design . the muslin material be very soft and wash well - better than many of the other a+a product I have buy , for some reason , which tend to pill up a lot more . the fit be great on my little one . he be get pretty strong at 6mo , and have not yet kick through it -lrb- as I read in some other review -rrb- even though it be a fairly thin material . yes , the material be lightweight - but perfect for daytime summer nap here in the SF Bay Area -lrb- daytime room temp of 68-72f -rrb- . this would not be a good purchase for nighttime use , or fall\/spring\/winter . the only thing that need improvement on this bag be the zipper . it be a little flimsy and the zipper have become separate a couple time . I have always be able to get it back on track fairly easily -lrb- so far -rrb- , but I have read in other review that the zipper have become irrevocably damage so be aware this may be a problem in the future .