The C91013 is the Pentax Close-Up Lens #3 for 49mm filter-screw size. It changes the focal length of the camera lens by +333 millimeters. In effect it makes the object much larger and much more detail is evident for critical evaluation.
In the Box
Pentax C91013 #3 Close-Up Lens Adapter for 49mm Filter CS-Mount Lenses increases Focal Length by 333mm