"Hold out your arm. That’s it." He measured Harry from shoulder to finger, then wrist to elbow, shoulder to floor, knee to armpit and round his head. As he measured, he said, "Every Ollivander wand has a core of a powerful magical substance, Mr. Potter. We use unicorn hairs, phoenix tail feathers, and the heartstrings of dragons. No two Ollivander wands are the same, just as no two unicorns, dragons, or phoenixes are quite the same. And of course, you will never get such good results with another wizard’s wand."