N52 water pumps: 11517586924 vs 11517586925-- what's the difference?

RealOEM has two water pumps listed: 11517586924 and 11517586925



http://ift.tt/R2w5qw



They're $150 different, so something is going on. Both seem to be currently sold, implying it's not one part superseding another (plus they're not listed as such). Both bring up pics via google image search that look identical.



So... what's going on here?