The internal soundness of lightweight materials can be evaluated by X-ray. Although it does not have as much penetrating power as gamma radiography for thicker, denser metals, X-ray is a very sensitive technique which can detect small, fine flaws such as cracking when oriented correctly. This is the method of choice when examining lighter metals such as aluminum or non-metallic materials such as fiberglass. X-ray tubes with capacities from 160kV to 400kV are available.