The 2.5 or the older 1.5?
The proline suspension is a nice upgrade. However, Id also take a look at the RPM suspension arms. They are a bit more durable and also come with a manufac replacement warrenty. We sell them at
www.rc-supply.com for 10.25 I think. But if you purchase all 4 at once we knock of an addition $7.00 .