Review on Hafisoe Wearable Blanket Oversized Sweatshirt by Katie Estabrook

It's so cute and I wanted to give it to my grandson for Christmas but I can't. Everything in it is wonderful. The only problem is that the description says two different sizes. My grandson needs a smaller size. The size listed at the top of this listing says "One Size"! Is it a smaller or larger size? There are no reviews that could indicate the age of the child. I need to find something else for him because if he arrives in a larger size it would be very disappointing for him at Christmas when his 2 siblings have to be the right size and have to wear theirs too, he isn't... :o(