OTG BIdriectional harddisk case: I still haven't found what I am looking for

I saw a OTG harddisk case which the store claimed to be supporting bidirectional copy (from memory card to Harddisk, and also from harddisk to memory card). The problem is that I cannot find any information about that case online, and my policy is that I will not buy anything that DOES NOT have information. Also I found the device at two stores. One store (at Golden Shopping Center, 62A Basement Floor) selling this "Motion DC Partner" for $330, and calim that it support bidirectional. But another store which sell it at $350 claimed that the device DOES NOT support bidirectioanl copy. However, that same salesman also claimed that bidirectional copy didn't even exist in the market, which totally destory his credibility of anything coming out of his mouth.

In fact, I am not sure what name the device is. Even though the sticker next the device on both store's shopping window says something like "Motion DC Partner" and "GA2400 Digital Partner", I didn't see any of those words on the device itself.

Well, I can always wait. I rather get a working device than being a testing object myself.