Now used for 109'ing Relic pieces. If you get these from dynamis, don't toss them! After about 50 minutes of casual farming, I had 12 of them with TH6.
The tanning vat recipe (x3) listed below isn't possible. These can only be crafted one at a time.
Also, it's not a 100% loss rate on the hide if you fail the synth, but the loss rate is very high (maybe ~95% or more) -- similar to the behemoth leather synth.