In need of a chain tension-er?? then here is a good source
Note the ones for $5 each plus an adapter so $6.60 each. The ones I use are 3 inches in diameter and have a BB hub. They are 1 inch wide and flat. IMO a V pulley will rub on the walls of the pulley and restrict chain movement sideways when shifting. I ordered 4 units. Used before and never any issues.