I saw a picture of a J frame with a cylinder that did not have the grooves on it. It was completely smooth. Is this an after market accessory? Who sells them?

Personally I thought it looked real cool. I am assuming there is no difference in performance-perhaps a little more weight.

Anyone had any experience with them?

Thanks,

Here is link to a picture (I know this one is a Ruger-but I saw one a a Smith J frame, but I can't find it now.)
http://ruger.com/Firearms/images/Products/122L.jpg