WD3200AAKS eSATA on zipzoomfly?

I'm trying to decide what hard drive to buy and I was interested in the Western Digital Caviar SE16 320GB. Newegg has an SATA 2.0 drive with the model WD3200AAKS. Zipzoomfly has the same model listed as a USB/eSATA drive. And their WD Caviar SE16 320GB has the model WD3200KS, which Newegg doesn't even list. I looked at Western Digital's site and it looked like WD3200AAKS is the correct model for the SATA 2.0 drive. I didn't even see anything for WD3200KS. So I'm just confused about what's going on with these models on zipzoomfly. I'm assuming it's a typo? Because wouldn't USB/eSATA make it an external hard drive, yet the picture looks like an internal hard drive to me. Yes, I want to save an extra $1 on zipzoomfly.