hey.. what kind of bikes are those in the video ??? ( may have to copy and past the link )

http://www.youtube.com/watch?v=xNMCdSOyvQY


I know there pit bikes but can you point me in the exact direction where to find something like that ?? and what there called exactly and what size they are ?? thnx

and any info about them that you know of

a link would be nice : )

thx