This set is an immensely useful reference for practicing anatomical drawing.
The quality is exceptionally good:
1) The technical quality is good, the image is of high resolution, it is neither very grainy nor blurred and the lighting is optimal. The background is not cluttered.
2) The model's posture is quite consistent. The ponytail helps to see ear and neck. A turntable with marks could be an option for an improvement, since the incremental turns are not 100% accurate, but that's a minor consideration.
This series of images is an outstanding free resource for beginners and may still be useful for professionals.