The SSX drive system can be added to any existing Skutt/Thomas Stuart electric wheel. This drive allows incredible sensitivity from the foot pedal at very low speeds. This drive system can be added to any of the Skutt electric wheels (except the Prodigy) at a later time but is more affordable when installed at the factory on your new wheel. All of the Skutt wheels on our website include this upgrade. If you would like the wheel without the SSX Upgrade please call 828-252-6033 or email firstname.lastname@example.org.