I'm surprised it's a 15 here in the UK, considering the "Hard R" hype from the makers (equivalent to an 18 rating here), but the description of the rating sounds what we would expect, so that's good. Interestingly, Predator 2 was re-rated from an original 18 down to a 15 in recent years. Perhaps the rating for Predator 1 will go down to a 15 once the new Blu-ray edition is released in a week or two. 18 rated films are more in line with the extreme graphic nature of the "Saw" franchise or movies that contain sex scenes.