P.I.D.s are commonly available in which lengths?

P.I.D. stands for Position-Indicating Device, which is an essential component in dental radiography, specifically for directing the X-ray beam accurately and minimizing patient exposure to radiation. The lengths most commonly used for P.I.D.s in dental practice are indeed 8 inches, 12 inches, and 16 inches.

Using these lengths helps to manage the area of exposure and reduces the volume of tissue irradiated, which is crucial for ensuring patient safety. The shorter 8-inch length is typically used for intraoral radiography and produces a larger beam, while the longer lengths, like 12 inches and 16 inches, allow for collimation and a more focused beam, which considerably lowers the patient's dose.

Therefore, the correct option reflects the standard lengths utilized in practice for providing safe and effective radiographic imaging.