I have the Miracle Blanket but there is only one size.
My DS will be 4 mo next 3rd august and it is a bit tight for him on the feet pocket (my lo is 7 kgs weight and 60 cms high), and besides the instructions of use say it's to be used with babies under 4 mo, but I might say I'll keep on using it because my baby's problem is not feet movement but arms' so when the pocket got too small I won't put his legs on it and will keep on swaddling him with the rest.