This kit is designed to Aid Equine Professionals achieve proper measurements for bone angles in X-rays of the equine hoof, as well as allowing the practitioner to properly line up an X-ray with a photograph of the same hoof and keep the scale / dimensions correct.  The cylinder has two ball bearings inside that are 90mm apart and will show up on the X-Ray. The 2 Finger Clips are for the photograph that gives a measurable 50mm line for scaling purposes.