Product review (5 stars): Did the job!
We have a Kitchenaid (Whirlpool) dishwasher that needed the replacement... with the help of the plethora YouTube videos (just search "dishwasher door balance replacement"), it was literally a five-minute job.  As described, the part fit perfectly.  We didn't need an extension like some other reviewers commented on, but apparently that's a semi-common need (a run up to Ace for a chain extension).