Measurements:
3M: neck hole 4", arm hole 3", leg hole 3", length (neck to bottom) 14.5", width (chest & waist) 7", arm span 12"
6M: neck hole 4.5", arm hole 3", leg hole 3" length (neck to bottom) 15", width (chest & waist) 8", armspan 14"
12M: neck hole 4.5", arm hole 4", length (neck to bottom) 16", width (chest & waist) 8.5", armspan 14"
18M: neck hole 5", arm hole 3.5", leg hole 4", length (neck to bottom) 16.5", width (chest & waist) 10", armspan 14.5"