Product review (4 stars): Adapt your Waste King to a sink designed for Insinkerators
This is the reason why you would NEED this adapter. Some sinks, like Elkay Perfect Drain, have welded-in flanges that are designed to work with Insinkerator disposers only. So, the only way to fit a Waste King EZ mount disposer is to use this adapter WITH an old Insinkerator quick mount. If you don't have this adapter and and an ISE quick mount, then you might as well buy an Insinkerator disposer for your Elkay Perfect Drain sink. Note that other brands of sink may offer similar welded flanges to Elkay's, but I haven't tried them yet.

So this product was great for my application, and installation worked out well. However, I'd also like to note that using this adapter will make your disposer sit a little bit lower than it's supposed to because you will essentially have two mounts connecting it to your drain: the ISE quick mount AND the Waste King EZ mount. That's just the way it works.