Actually looked at them specifically.
They are in line with the cheap battery sites, & appear to be no worse than others for warranty.
On further digging I found pretty mixed reviews. For example.
https://www.trustpilot.com/review/batterysharks.comIn the end I just bought a YUASA online that I added the acid to myself & gave the initial charge & have had no regrets over the last few years.
Since that worked out I've continued doing so.
Like with all things bikish, you can get some decent stuff out of China, but if the price is real special you can bet that $$ was saved somewhere.