Product review (5 stars): Awful thing but required
This is a lousy design, poorly made, and essential to keep your piece-of-crap Whirlpool/KitchenAid dishwasher running. Somewhat hard to install, you get better with the practice you will almost certainly get since your dishwasher is, as mentioned, rubbish. The chopper assembly is supposed to prevent large bits of food from clogging the pump (a problem, oddly, never encountered in our 30 year old model.) In my experience this device lasts around one year, then becomes a "hey, let's use these dull blades to shove food firmly into the screen so it can be totally clogged" device.

However, if you want to use the top rack of your dishwasher, this is the part you have to replace. You can do it yourself using on-line instructions available in a few different places. It's not that easy but it's not impossible either and avoids a $300 service call (that's $100 for the first hour and $200 to show up. Maybe your service people are cheaper. I sure hope so.)

(Why four stars? Because you can buy it here for a fraction of the price of having a repairman.)

UPDATE: Its now lasted nearly a year. Thats far better than the original one.