The new pulley is in fact smaller. The new pulley has to have a bearing and I wanted to use a easy to get part so I chose this genuine nissan idler pulley. The diameter is 1" smaller so I relocated the hole for the main bolt to be able to use the stock length belt. Joel W. RTR >Neat. Why does the pulley on your eliminator, though, appear smaller >than the pulley on the pump next to it? Just curious.