I agree with the previous posters--this costume is pretty poorly made, and certainly will not withstand repeated play from my six-year-old.  The belt fits ME.  We just used some velcro strips (like you would use to contain cords) and folded part of the back of the belt up.  Worked fine.  The velcro to close the belt has already partially come off (after simply trying on the costume).  The shirt is VERY thin.  My son normally wears a size 5, and the costume otherwise fits him fine.  He loves the costume, however, and feels "cool" in it.  It's not worthy of the "deluxe" title they give it, but for the coolness factor and if you're willing to fork over the cash, it's worth it.

*Review edited to describe durability (or lack thereof)--the shoulder seams and some of the arm seams are coming apart, after Halloween night (2nd time wearing the costume; first time for 2 hours).  The fabric is so thin, it's like gauze.  I plan to sew the seams back together, but the fabric is fraying so badly that it will have to  be taken in a bit.  Terrible quality.