This is the officially  licensed Wolverine Deluxe Muscle Costume for Children from X-Men.

Wolverine Deluxe Muscle Childs Costume comes with muscle torso jumpsuit with attached boot tops, pair of claws, belt buckle and foam mask.

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This is the size information provided by the manufacturer:

• 4-6
  Fits Chest 23"-25", Waist 21"-22", Hips 23"-25", Inseam 16"-19", Height 39"-47", Weight 36-47 lbs.

• 7-8
  Fits Chest 26"-27", Waist 23"-24", Hips 25"-27", Inseam 20"-22", Height 48"-51", Weight 48-60 lbs.