I just recently purchased this for my 3 month old. She was fully swaddled since birth so I was very skeptical how well this would do. I am amazed at how well she took to it, from the very first night. I just purchased a size bigger and soon I will purchase the regular weighted swaddle with no arms. The weighted transition swaddle helps with her involuntary moves during the night while she sleeps so it helps her stay sleeping. She has gotten more sleep and so have I!