Instruction: Answer the given question using the supporting document.

Input:
Question: I'm assuming this also works with a Casio CTK-573 model?
Document: At the time of purchase, the CTK-500 was not specifically listed as compatible with this adapter. I took a chance, though, and was pleased to find that it is the appropriate adapter for this model. I'm very glad to see that it's still possible to obtain needed parts for keyboards from the 80s and 90s!
We lost the power adapter for our Casio CTK-573 keyboard, and this one is a perfect replacement.
Excellent price, quick shipping and works perfectly. Box states this adapter also fits the following keyboards:For All LK Models, All CTK Models (Except CTK-5000) and for these WK Models:  WK-110 and WK-200Input:  AC100-240V~50/60HzOutput: DC9V --- 840mA
When I ordered the Casio SA-67 keyboard on 11/05/02, I also ordered the Casio AD-5UL AC adapter at your recommedation, along with other items. I held the items till Christmas for our grandson when we were disapointed to find that the plug on the AD-5UL adapter was too large for the DC7.5V jack on the electronic keyboard. The keyboard user's guide clearly specifies the model AD-1 as the only AC adaptor to be used with the SA-67 keyboard.
After losing the adapter months ago, I've been searching for one that would fit my CTK-720 keyboard and this was definitely worth the money. The adapter is smaller than the original adapter but it fits and works very well. I definitely recommend it, just make sure that your model is compatible with the adapter before purchase.
Amazing, I read all the reviews and "assumed" the problem with the wrong adapter was resolved since reviewers have complained since 2003. I ordered the Casio CTK 691 keyboard, clicked on the recommended power adapter and trusted the folks at Amazon knew which model I would need. Wrong, it doesn't fit. Since we bought this keyboard to travel this summer it has been very inconvenient, and we haven't had time to resolve it.
I received my father's Casio CA-100 keyboard a few months after he passed away, but the power adapter was missing and it had to be a specific item in order to work. Although the keyboard was at least 18 years old and not sold anymore, I found the adapter on Amazon and now it works beautifully. My dad was very musical and I'm glad to have something of his that he enjoyed and that I can enjoy too.
What can you say about a power adapter? It works. It's Casio, not a knock-off brand. There is nothing to fear, as long as it is the correct model number for what you need to power.
I bought this to go with the Casio CTK-2100 keyboard after reading the reviews. Glad I did. It fits and works perfectly.
After reading some of the issues people are having with incompatible adapters, I was worried. However, mine came and I've had no problems. Just wanted to let you know that it works for Casio CTK-3000!
Answer: My understanding was that it worked with all CTK models. That is the best I can offer :)