The RigiScan requires two tension guides (one Base Tension Guide and one Tip Tension Guide) in order to conduct patient testing. The Tip Tension Guide has white indicators so that it can be differentiated from the Base Tension Guide. The RigiScan instrument should not be used if the tension guides are worn or damaged as this could result in patient discomfort or injury. RigiScan users should inspect the tension guides regularly and replace them promptly if damage is detected. Note that federal law restricts the RigiScan instrument to use by, or on order of a physician. As a result, this product is only available for sale to medical professionals.