ShareCFinex is a March 2018 launced cryptocurrency exchange based in Hong Kong and it doesn't forbid US investors from using its services.
CFinex has about eight trading pairs and supports only six cryptocurrencies with a daily varying trading volume.
CFinex doesn't allow you to deposit fiat either through wire transfer or credit and debit cards, it only takes cryptocurrency.
CFinex charges you 0.002btc for withdrawal fees and 0.25% flat rate trading fees as taker and maker, and going by the industry's average it is out of line.
This I hereby submit that CFinex is no more in existence as it made a public announcement via its twitter social channel that it was shutting down in October of the same year it was released so therefore stay guarded and guided against fraudsters.