Just for reference, there are two idlers.... the SC idler(65mm?) that sits just to the left of the SC pulley and the Idler pulley(90mm?) that sits above the water pump pulley.... the SC Idler is plastic and the Idler is steel.

FYI, the idler pulley is the same size and configuration as the tensioner pulley. If your tensioner pulley bearing goes out, just get an idler pulley to replace it as it is cheaper than having to buy the new tensioner assembly.