What does a classic cam shaft belt tensioner look like?
 

I'm going to be getting my cam belt changed and while it's being swapped i was thinking of maybe getting a pulley kit. I've been told you need a tensioner/s (Is it just one?) when you change the cam belt and the pulley kit i was looking at comes with a tensioner:

CDF Racing Suppliers of Whiteline bailey manley wiseco samco powerflex performance fricton

Is this something else or is this an actual tensioner?

Thanks

Ignore please.