The Kindle SportGrip is a soft rubberised cover which fits perfectly over my Kindle with easy access to all the buttons. It provides protection to the corners and the back, but not to the front of the Kindle which is open to the elements. However, it does not provide as much protection as a proper leather type case which would be more resistant to, for example, the Kindle being dropped.
The cover has a nice, non slip feel to it and is quite light. I am not sure what sports the manufacturers had in mind for its use, but it's fine in the gym on the static bikes etc. There are drawbacks in terms of looks and lack of protection when compared with some of Marware's more all encompassing covers but I am not sure there are any obvious advantages.