One key point to note here, except for the tiny size, is that there is no cap which you can lose. The contacts seem to be very rugged, so there's no need for extra protection.
The backside is just black plastic. If you look at the high-res version you can see a tiny gap from where the case has been closed during the manufacturing process. This doesn't look waterproof, a bit of water spillage shouldn't be a problem though.
For size comparison I placed the OCZ Rally and the OCZ Mini Kart on a CD. The OCZ Rally is already one of the smallest "regular sized" USB sticks. But compared to the Mini Kart it is huge.
When the USB stick is in use a small LED on the backside is lit. During accesses it starts to blink.
Wow. Isn't that pretty. The Mini Kart looks like it was made to go together with my notebook.
Given the small size of this USB stick it is well possible carrying it in your wallet. Also noteworthy is that it is extremely light weight because of the all-plastic case. On the other hand this gives it a bit of a cheap touch since you can barely feel the weight in your hands.