Ack! I looked at the file and it is a design flaw on my part. I am so, so sorry! (This is a very old set; one of my first.) I revised the helmet to have a deeper cavity at some point (which is why x01618's version fits better), but I must not have updated this particular page. (So, I've just updated the file now.) However, if you plan on ordering something from my shop in the future, I can "bundle" the helmet with one of those items. I won't include the markup on the helmet. (Alternatively, you could see if Shapeways will give you a refund.) My apologies, again, and thanks for bringing it to my attention!