Futaba Japan released a notification last week that it's come to their attention there are counterfeit Futaba products on the market. Particularly the Futaba GY401 Gyro and Futaba S9254 tail servo are noted in the release. These products will obviously not have the same performance as genuine Futaba products.
The key thing to look for is the color of the pins in the servo connector. All Futaba products have gold pins in the connectors. The counterfeit products have silver pins. Another tell tell sign is the length of the grommet on the servo lead exiting the servo case. If the grommet is shorter then normal, it's a sign of a counterfeit.
These counterfeit products are typically sold out of Hong Kong and other parts of China, and are prolific on eBay. I highly suggest you purchase from authorized dealers and resellers. If the price is too good to be true, it usually is for a reason!
Here is a translation from Google Translate.