ive looked and looked trying to find an answer to this but no luck. the only luck i had a was a guy said his came setup as hammerhead and it was too fast so he needed to change it to the barracuda. in a pic he appeared to be installing the gray impeller. he said it was still too fast for him after the swap so im assuming he was correct and it slowed but not enough. so, based on all the pictures with the gray impeller sitting next to it, i would say the gray is the barracuda/4680. you could always throw it in a tub and look for a noticable difference.