Casper had a gel-infused foam topper, and then they were designing their own latex one. It was discussed in a few placed here on the forum - check this thread out. If you’re replacing your old one are you able to simply measure it to find out the thickness, or is your old one gone? You could look on the law tag to determine the foam content and whether yours was latex or not. I personally don’t have any more specifics, but maybe someone else on the forum does.
Added: I contacted Casper directly (they have a chat function on their web site in case you weren’t aware) and they stated it was 2" thick and the latex version was close to this.