A distractor is a surgical instrument used to separate, retract, or hold open tissues, bones, or structures during a procedure. A set ranging from 7 mm to 15 mm likely refers to an orthopedic or spinal distractor set, where the numbers indicate the size of the interchangeable tips or the distraction distance. This allows the surgeon to choose the appropriate size for different anatomical requirements.

These instruments create and maintain space between bones, joints, or vertebrae, enabling access and visualization for the surgeon.