Jazz strings differ from the other sets by having a wound G-string (like the three thicker strings in a regular electric set). At the moment Jazz strings are available in one gauge. However, there are plenty of ways to combine your own sets in "Single Strings/Customize Sets" in the menu

Description:
Jazz set - .012 .016 .022 .032 .042 .052

If none of the above sets fit your desired string balance you can choose "Single Strings/Customize Sets" in the menu on the left...

Stringsite.com's strings are all Electric Nickel Wound which concist of a steel alloy plated with nickel. This method of manufacturing brings several advantages: The strings get a nice crisp and "round" sound as well as being more consistent and restistant to oxidation (rust) than 100% steel strings. Finally the nickel plating provides a softer feel to the strings which reduce finger noise (screech when moving across the strings) and also give longer life to both strings and frets.