DavisDVD has put up a quick guide as to what are the specific differences between the rated and unrated cuts of Alexandre Aja’s ballsy Hills remake. 

The differences* are pretty minor and I’d say relatively unimportant - if the MPAA doesn’t want a gun pointed at a baby’s face, Colic has no chance in America’s bully censorship rings - but it’s an interesting breakdown of just how slight the gradient is between an R cut and NC-17.

DavisDVD Hills Have Eyes Unrated DVD comparison

*If you haven’t seen the ‘rated’ theatrical cut yet, there will be slight spoilage.